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Sample records for light sn isotopes

  1. Nucleon pairing in Sn isotopes

    NASA Astrophysics Data System (ADS)

    Imasheva, L.; Ishkhanov, B.; Stepanov, M.; Tretyakova, T.

    2016-01-01

    The systematics of excited states in Sn isotopes are discussed on basis of pairing interaction in nuclei. Nucleon paring leads to formation of excited states multiplets. The estimation of multiplet splitting based on experimental nuclear masses allows one to calculate the position of excited states with different seniority in δ-approximation. The wide systematics of the spectra of Sn isotopes gives a possibility to check the pairing interaction for different subshells and consider the multiplets of excited states in the neutron-rich isotopes far from stability.

  2. Quadrupole Collectivity in Neutron Deficient Sn Isotopes

    NASA Astrophysics Data System (ADS)

    Gade, Alexandra

    2014-03-01

    One of the overarching goals of nuclear physics is the development of a comprehensive model of the atomic nucleus with predictive power across the nuclear chart. Of particular importance for the development of nuclear models is experimental data that consistently track the effect of isospin and changed binding, for example. The chain of Sn isotopes has been a formidable testing ground for nuclear models as some spectroscopic data is available from N = Z = 50 100Sn in the proximity of the proton dripline to 134Sn, beyond the very neutron-rich doubly magic nucleus 132Sn. In even-even nuclei, the electromagnetic quadrupole excitation strength is a measure of quadrupole collectivity, sensitive to the presence of shell gaps, nuclear deformation, and nucleon-nucleon correlations, for example. In the Sn isotopes, this transition strength has been reported from 104Sn to 130Sn, spanning a chain of 14 even-even Sn isotopes. The trend is asymmetric with respect to midshell and not even the largest-scale shell-model calculations have been able to describe the evolution of transition strength across the isotopic chain without varying effective charges. Implications will be discussed. This work was supported by the National Science Foundation under Grant No. PHY-1102511.

  3. Shell model calculation for Te and Sn isotopes in the vicinity of {sup 100}Sn

    SciTech Connect

    Yakhelef, A.; Bouldjedri, A.

    2012-06-27

    New Shell Model calculations for even-even isotopes {sup 104-108}Sn and {sup 106,108}Te, in the vicinity of {sup 100}Sn have been performed. The calculations have been carried out using the windows version of NuShell-MSU. The two body matrix elements TBMEs of the effective interaction between valence nucleons are obtained from the renormalized two body effective interaction based on G-matrix derived from the CD-bonn nucleon-nucleon potential. The single particle energies of the proton and neutron valence spaces orbitals are defined from the available spectra of lightest odd isotopes of Sb and Sn respectively.

  4. Inelastic proton scattering of Sn isotopes studied with GRETINA

    NASA Astrophysics Data System (ADS)

    Campbell, Christopher

    2014-03-01

    The chain of semi-magic Sn nuclei, with many stable isotopes, has been a fertile ground for experimental and theoretical studies. Encompassing a major neutron shell from N = 50 to 82, the properties and structure of these nuclei provided important data for the development of the pairing-plus-quadrupole model. Recent experimental information on B(E2) for 106,108,110,112Sn came as a surprise as it indicated a larger collectivity than the predicted parabolic trend of quadrupole collectivity. These data, instead, show an unexpectedly flat trend even as the number of valence particles is reduced from 12 to 6. To fully understand how collectivity is evolving in these isotopes, 108,110,112Sn have been studied using thick-target, inelastic proton scattering with GRETINA tagging inelastic scattering events by detecting gamma-rays from the prompt decay of states excited in the reaction. We will present the trend of 2 + excitation cross-sections, the deduced quadrupole deformation parameters, and observations of other low-lying collective states. Comparison of these (p,p') quadrupole deformation parameters with B(E2) data will provide new insights into the relative importance of proton and neutron contributions to collectivity in these nuclei. GRETINA was funded by the US DOE - Office of Science. Operation of the array at NSCL is supported by NSF under Cooperative Agreement PHY-1102511(NSCL) and DOE under grant DE-AC02-05CH11231(LBNL).

  5. Application of (119)Sn CPMG MAS NMR for Fast Characterization of Sn Sites in Zeolites with Natural (119)Sn Isotope Abundance.

    PubMed

    Kolyagin, Yury G; Yakimov, Alexander V; Tolborg, Søren; Vennestrøm, Peter N R; Ivanova, Irina I

    2016-04-01

    (119)Sn CPMG MAS NMR is demonstrated to be a fast and efficient method for characterization of Sn-sites in Sn-containing zeolites. Tuning of the CPMG echo-train sequence decreases the experimental time by a factor of 5-40 in the case of as-synthesized and hydrated Sn-BEA samples and by 3 orders of magnitude in the case of dehydrated Sn-BEA samples as compared to conventional methods. In the latter case, the reconstruction of the quantitative spectrum without the loss of sensitivity is shown to be possible. The method proposed allows obtaining (119)Sn MAS NMR spectra with improved resolution for Sn-BEA zeolites with natural (119)Sn isotope abundance using conventional MAS NMR equipment. PMID:26978430

  6. New lifetime measurements in the stable semimagic Sn isotopes using the Doppler-shift attenuation technique

    NASA Astrophysics Data System (ADS)

    Jungclaus, A.; Walker, J.; Leske, J.; Speidel, K.-H.; Stuchbery, A. E.; East, M.; Boutachkov, P.; Cederkäll, J.; Doornenbal, P.; Egido, J. L.; Ekström, A.; Gerl, J.; Gernhäuser, R.; Goel, N.; Górska, M.; Kojouharov, I.; Maier-Komor, P.; Modamio, V.; Naqvi, F.; Pietralla, N.; Pietri, S.; Prokopowicz, W.; Schaffner, H.; Schwengner, R.; Wollersheim, H.-J.

    2011-09-01

    Precise measurements of lifetimes in the picosecond range of excited states in the stable even-A Sn isotopes 112,114,116,122Sn have been performed using the Doppler shift attenuation technique. For the first excited 2+ states in 112Sn, 114Sn and 116Sn the E2 transition strengths deduced from the measured lifetimes are in disagreement with the previously adopted values. They indicate a shallow minimum at N = 66 in contrast to the maximum at mid-shell predicted by modern shell model calculations.

  7. Preparation of α-SnWO4/SnO2 heterostructure with enhanced visible-light-driven photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Yao, Shiyue; Zhang, Min; Di, Junwei; Wang, Zuoshan; Long, Yumei; Li, Weifeng

    2015-12-01

    In this work, a novel α-SnWO4/SnO2 heterostructure was synthesized via a facile two-step hydrothermal method. The as-prepared products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scan electron microscopy (SEM) and transmission electron microscopy (TEM), which confirmed the typical orthorhombic α-SnWO4 phase, plate-like morphology and α-SnWO4/SnO2 heterostructure. The photocatalytic studies revealed that the attachment of SnO2 nanoparticles on the surface of α-SnWO4 plates can remarkably improve their photocatalytic activities and the α-SnWO4/SnO2 heterostructure exhibited the best photocatalytic properties in the degradation of methyl orange (MO) under visible light irradiation. The degradation rate of MO on α-SnWO4/SnO2 plate was 97% within 40 min and the photocatalytic degradation reaction followed the pseudo-first-order kinetics. The enhanced photocatalytic property was ascribed to the large surface area and the heterojuction between α-SnWO4 and SnO2, which can facilitate efficient charge separation of photogenerated electron-hole pairs. Furthermore, α-SnWO4/SnO2 nanocomposite demonstrated good recyclability, which is useful for its practical application.

  8. Fabrication of SnO2@SnS2 heterostructure with enhanced visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chen, Haitao; Gu, Ming; Pu, Xuemei; Zhu, Jun; Cheng, Liwen

    2016-06-01

    SnO2@SnS2 heterojunction structures have been successfully fabricated by hydrothermal oxidation of SnS2 nanoparticles in H2O2 aqueous solution. The structure and photodegradation activity of the SnO2@SnS2 heterojunction were characterized. Results indicated that SnO2@SnS2 nanocomposite exhibited enhanced photocatalytic activities compared to pure SnS2 and SnO2 under visible-light irradiation. Based on the analysis of the related energy structures, a coupled band gap structure mode was proposed. It is believed that the tight heterojunction structure and the coupled band gap structure play important roles in facilitating interfacial electron transfer and in reducing self-radiative recombination of charges.

  9. Calculation of the ground state properties of even-even Sn isotopes

    SciTech Connect

    Aytekin, H. Baldik, R.; Tel, E.

    2010-06-15

    We investigate the ground-state properties of even-even Sn isotopes using the Skyrme-Hartree-Fock (SHF) and Skyrme-Hartree-Fock-Bogolyubov (SHFB) methods with SKM* and SLy4 force parameters. We focus on isotopes of even-even Sn because these isotopes are vital to the structural studies of unstable nuclei taking place at the electron radioactive-ion collider at RIKEN. In the present paper, we calculate the binding energies per particle, the rms nuclear charge radii, the rms nuclear proton density radii, and the rms nuclear neutron density radii, for even-even Sn isotopes, using the SHF and SHFB methods. We compare our results with experimental data and with the results of relativistic mean-field theory. Notably, we fit our calculated binding energies per particle to experimental results, using the aforementioned SHF methods with SKM* and SLy4 parameters

  10. Light echoes and transient luminescence near SN 1987A

    NASA Technical Reports Server (NTRS)

    Crotts, Arlin P. S.; Kunkel, William E.; Mccarthy, Patrick J.

    1989-01-01

    The discovery of two new light echoes from sheets of material behind supernova 1987A and present images of the progenitor's circumstellar shell are reported, indicating diffuse echoes from the star's red giant wind. The echo sheets' geometry explains well the behavior of SN 1987's 10-micron flux, but the circumstellar shell appears to be 70 percent larger than the prediction from the analysis of narrow UV emission lines. The sheets' recombination time show them relatively thin and dense. The data also constrain the existence of any fourth star in the Sanduleak -69 deg 202 system and show that the feature reported 8 arcsecs from the supernova is probably not an echo from a thin sheet in SN 1987A's foreground.

  11. Evolution of the pygmy dipole resonance in Sn isotopes

    NASA Astrophysics Data System (ADS)

    Toft, H. K.; Larsen, A. C.; Bürger, A.; Guttormsen, M.; Görgen, A.; Nyhus, H. T.; Renstrøm, T.; Siem, S.; Tveten, G. M.; Voinov, A.

    2011-04-01

    Nuclear level density and γ-ray strength functions of Sn121,122 below the neutron separation energy are extracted with the Oslo method using the (He3,He3'γ) and (He3,αγ) reactions. The level densities of Sn121,122 display steplike structures, interpreted as signatures of neutron pair breaking. An enhancement in both strength functions, compared to standard models for radiative strength, is observed in our measurements for Eγ≳5.2 MeV. This enhancement is compatible with pygmy resonances centered at ≈8.4(1) and ≈8.6(2) MeV, respectively, and with integrated strengths corresponding to ≈1.8-5+1% of the classical Thomas-Reiche-Kuhn sum rule. Similar resonances were also seen in Sn116-119. Experimental neutron-capture cross reactions are well reproduced by our pygmy resonance predictions, while standard strength models are less successful. The evolution as a function of neutron number of the pygmy resonance in Sn116-122 is described as a clear increase of centroid energy from 8.0(1) to 8.6(2) MeV, but with no observable difference in integrated strengths.

  12. Alpha-decay of light protactinium isotopes

    SciTech Connect

    Faestermann, T.; Gillitzer, A.; Hartel, K.; Henning, W.; Kienle, P.

    1987-12-10

    Light protactinium isotopes have been produced with /sup 204/Pb (/sup 19/F,xn) reactions. ..cap alpha..-activities with E/sub ..cap alpha../ = 9.90(5) MeV, T/sub 1/2/ = 53(10) ns and E/sub ..cap alpha../ = 9.65(5) MeV, T/sub 1/2/ = 0.78(16) ..mu..s could be attributed to the previously unobserved nuclei /sup 219/Pa and /sup 220/Pa with the help of excitation functions. The peak cross sections for the 4n and 3n evaporation channels are on the order of 10 ..mu..b. The decay energies as well as the halflives fit well into the systematics of these nuclei close to the magic neutron number N = 126. /sup 219/Pa is the shortest lived nuclide known with directly measured halflife.

  13. Fusion reactions in collisions induced by Li isotopes on Sn targets

    SciTech Connect

    Fisichella, M.; Shotter, A. C.; Di Pietro, A.; Figuera, P.; Lattuada, M.; Marchetta, C.; Musumarra, A.; Pellegriti, M. G.; Ruiz, C.; Scuderi, V.; Strano, E.; Torresi, D.; Zadro, M.

    2012-10-20

    Fusion cross sections for the {sup 6}Li+{sup 120}Sn and {sup 7}Li+{sup 119}Sn systems have been measured. We aim to search for possible effects due to the different neutron transfer Q-values, by comparing the fusion cross sections for the two systems below the barrier. This experiment is the first step of a wider systematic aiming to study the above problems in collisions induced by stable and unstable Li isotopes on tin all forming the same compound nucleus.

  14. New Isotopes and Proton Emitters-Crossing the Drip Line in the Vicinity of 100Sn

    NASA Astrophysics Data System (ADS)

    Čeliković, I.; Lewitowicz, M.; Gernhäuser, R.; Krücken, R.; Nishimura, S.; Sakurai, H.; Ahn, D. S.; Baba, H.; Blank, B.; Blazhev, A.; Boutachkov, P.; Browne, F.; de France, G.; Doornenbal, P.; Faestermann, T.; Fang, Y.; Fukuda, N.; Giovinazzo, J.; Goel, N.; Górska, M.; Ilieva, S.; Inabe, N.; Isobe, T.; Jungclaus, A.; Kameda, D.; Kim, Y.-K.; Kwon, Y. K.; Kojouharov, I.; Kubo, T.; Kurz, N.; Lorusso, G.; Lubos, D.; Moschner, K.; Murai, D.; Nishizuka, I.; Park, J.; Patel, Z.; Rajabali, M.; Rice, S.; Schaffner, H.; Shimizu, Y.; Sinclair, L.; Söderström, P.-A.; Steiger, K.; Sumikama, T.; Suzuki, H.; Takeda, H.; Wang, Z.; Watanabe, H.; Wu, J.; Xu, Z.

    2016-04-01

    Several new isotopes, 96In, 94Cd, 92Ag, and 90Pd, have been identified at the RIKEN Nishina Center. The study of proton drip-line nuclei in the vicinity of 93Ag and 89Rh with half-lives in the submicrosecond range. The systematics of the half-lives of odd-Z nuclei with Tz=-1 /2 toward 99Sn shows a stabilizing effect of the Z =50 shell closure. Production cross sections for nuclei in the vicinity of 100Sn measured at different energies and target thicknesses were compared to the cross sections calculated by epax taking into account contributions of secondary reactions in the primary target.

  15. Analogous intruder behavior near Ni, Sn, and Pb isotopes

    NASA Astrophysics Data System (ADS)

    Liddick, S. N.; Walters, W. B.; Chiara, C. J.; Janssens, R. V. F.; Abromeit, B.; Ayres, A.; Bey, A.; Bingham, C. R.; Carpenter, M. P.; Cartegni, L.; Chen, J.; Crawford, H. L.; Darby, I. G.; Grzywacz, R.; Harker, J.; Hoffman, C. R.; Ilyushkin, S.; Kondev, F. G.; Larson, N.; Madurga, M.; Miller, D.; Padgett, S.; Paulauskas, S. V.; Rajabali, M. M.; Rykaczewski, K.; Seweryniak, D.; Suchyta, S.; Zhu, S.

    2015-08-01

    Near shell closures, the presence of unexpected states at low energies provides a critical test of our understanding of the atomic nucleus. New measurements for the N =42 isotones Co6927 and Cu7129, along with recent data and calculations in the Ni isotopes, establish a full set of complementary, deformed, intruder states astride the closed-shell 28Ni isotopes. Nuclei with a one-proton hole or one-proton particle adjacent to Z =28 were populated in β -decay experiments and in multinucleon transfer reactions. A β -decaying isomer, with a 750(250)-ms half-life, has been identified in 42,27,69Co. It likely has low spin and accompanies the previously established 7 /2- state. Complementary data for the levels of isotonic 42,29,71Cu support the presence of a deformed, Δ J =1 band built on the proton intruder 7 /2- level at 981 keV. These data, together with recent studies of lower-mass Co and Cu isotopes and extensive work near 68Ni, support the view that intruder states based on particle-hole excitations accompany all closed proton shells with Z ≥28 .

  16. New Isotopes and Proton Emitters-Crossing the Drip Line in the Vicinity of ^{100}Sn.

    PubMed

    Čeliković, I; Lewitowicz, M; Gernhäuser, R; Krücken, R; Nishimura, S; Sakurai, H; Ahn, D S; Baba, H; Blank, B; Blazhev, A; Boutachkov, P; Browne, F; de France, G; Doornenbal, P; Faestermann, T; Fang, Y; Fukuda, N; Giovinazzo, J; Goel, N; Górska, M; Ilieva, S; Inabe, N; Isobe, T; Jungclaus, A; Kameda, D; Kim, Y-K; Kwon, Y K; Kojouharov, I; Kubo, T; Kurz, N; Lorusso, G; Lubos, D; Moschner, K; Murai, D; Nishizuka, I; Park, J; Patel, Z; Rajabali, M; Rice, S; Schaffner, H; Shimizu, Y; Sinclair, L; Söderström, P-A; Steiger, K; Sumikama, T; Suzuki, H; Takeda, H; Wang, Z; Watanabe, H; Wu, J; Xu, Z

    2016-04-22

    Several new isotopes, ^{96}In, ^{94}Cd, ^{92}Ag, and ^{90}Pd, have been identified at the RIKEN Nishina Center. The study of proton drip-line nuclei in the vicinity of ^{100}Sn led to the discovery of new proton emitters ^{93}Ag and ^{89}Rh with half-lives in the submicrosecond range. The systematics of the half-lives of odd-Z nuclei with T_{z}=-1/2 toward ^{99}Sn shows a stabilizing effect of the Z=50 shell closure. Production cross sections for nuclei in the vicinity of ^{100}Sn measured at different energies and target thicknesses were compared to the cross sections calculated by epax taking into account contributions of secondary reactions in the primary target. PMID:27152796

  17. GeSn waveguide structures for efficient light detection and emission

    NASA Astrophysics Data System (ADS)

    Lin, You-Long; Huang, Yu-Hui; Chen, Shao-Wei; Chang, Guo-En

    2015-02-01

    We report the fabrication and characterization of GeSn waveguide structures on Si substrates grown by molecular beam epitaxy for efficient light-detection and emission. For photodetectors, GeSn waveguide structures exhibit a higher optical response compared to a reference Ge device as revealed by the photocurrent experiments. For light-emission, room-temperature photoluminescence experiments show a redshifted emission wavelength for the GeSn samples compared to the Ge reference sample due to the Sn incorporation. Besides, we observe ripple characteristics in the amplified spontaneous emission spectrum of the GeSn waveguide structure, which are attributed to the waveguide modes. Those results suggest that GeSn waveguide structures are promising for high-performance Si-based lightdetectors and emitters integrable with Si electronics.

  18. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    DOE PAGESBeta

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; Wrzesiński, J.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; et al

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudesmore » for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.« less

  19. E2 transition probabilities for decays of isomers observed in neutron-rich odd Sn isotopes

    SciTech Connect

    Iskra, Ł. W.; Broda, R.; Janssens, R. V.F.; Wrzesiński, J.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Zhu, S.

    2015-01-01

    High-spin states were investigated with gamma coincidence techniques in neutron-rich Sn isotopes produced in fission processes following ⁴⁸Ca + ²⁰⁸Pb, ⁴⁸Ca + ²³⁸U, and ⁶⁴Ni + ²³⁸U reactions. By exploiting delayed and cross-coincidence techniques, level schemes have been delineated in odd ¹¹⁹⁻¹²⁵Sn isotopes. Particular attention was paid to the occurrence of 19/2⁺ and 23/2⁺ isomeric states for which the available information has now been significantly extended. Reduced transition probabilities, B(E2), extracted from the measured half-lives and the established details of the isomeric decays exhibit a striking regularity. This behavior was compared with the previously observed regularity of the B(E2) amplitudes for the seniority ν = 2 and 3, 10⁺ and 27/2⁻ isomers in even- and odd-Sn isotopes, respectively.

  20. HELIX: The High Energy Light Isotope Experiment

    NASA Astrophysics Data System (ADS)

    Tarle, Gregory

    This is the lead proposal for a new suborbital program, HELIX (High-Energy Light Isotope eXperiment), designed to make measurements of the isotopic composition of light cosmic-ray nuclei from ~200 MeV/nuc to ~10 GeV/nuc. Past measurements of this kind have provided profound insights into the nature and origin of cosmic rays, revealing, for instance, information on acceleration and confinement time scales, and exposing some conspicuous discrepancies between solar and cosmic-ray abundances. The most detailed information currently available comes from the ACE/CRIS mission, but is restricted to energies below a few 100 MeV/nuc. HELIX aims at extending this energy range by over an order of magnitude, where, in most cases, no measurements of any kind exist, and where relativistic time dilation affects the apparent lifetime of radioactive clock nuclei. The HELIX measurements will provide essential information for understanding the propagation history of cosmic rays in the galaxy. This is crucial for properly interpreting several intriguing anomalies reported in recent cosmic-ray measurements, pertaining to the energy spectra of protons, helium, and heavier nuclei, and to the anomalous rise in the positron fraction at higher energy. HELIX employs a high-precision magnet spectrometer to provide measurements which are not achievable by any current or planned instrument. The superconducting magnet originally used for the HEAT payload in five successful high-altitude flights will be combined with state-of-the-art detectors to measure the charge, time-of-flight, magnetic rigidity, and velocity of cosmic-ray particles with high precision. The instrumentation includes plastic scintillators, silicon-strip detectors repurposed from Fermilab's CDF detector, a high-performance gas drift chamber, and a ring-imaging Cherenkov counter employing aerogel radiators and silicon photomultipliers. To reduce cost and technical risk, the HELIX program will be structured in two stages. The first

  1. Photocatalytic Degradation of Isopropanol Over PbSnO3 Nanostructures Under Visible Light Irradiation

    NASA Astrophysics Data System (ADS)

    Chen, Di; Ouyang, Shuxin; Ye, Jinhua

    2009-03-01

    Nanostructured PbSnO3 photocatalysts with particulate and tubular morphologies have been synthesized from a simple hydrothermal process. As-prepared samples were characterized by X-ray diffraction, Brunauer-Emmet-Teller surface area, transmission electron microscopy, and diffraction spectroscopy. The photoactivities of the PbSnO3 nanostructures for isopropanol (IPA) degradation under visible light irradiation were investigated systematically, and the results revealed that these nanostructures show much higher photocatalytic properties than bulk PbSnO3 material. The possible growth mechanism of tubular PbSnO3 catalyst was also investigated briefly.

  2. Gamma-ray emission from SN2014J near maximum optical light

    NASA Astrophysics Data System (ADS)

    Isern, J.; Jean, P.; Bravo, E.; Knödlseder, J.; Lebrun, F.; Churazov, E.; Sunyaev, R.; Domingo, A.; Badenes, C.; Hartmann, D. H.; Hoeflich, P.; Renaud, M.; Soldi, S.; Elias-Rosa, N.; Hernanz, M.; Domínguez, I.; García-Senz, D.; Lichti, G. G.; Vedrenne, G.; Von Ballmoos, P.

    2016-04-01

    Context. The optical light curve of Type Ia supernovae (SNIa) is powered by thermalized gamma-rays produced by the decay of 56Ni and 56Co, the main radioactive isotopes synthesized by the thermonuclear explosion of a C/O white dwarf. Aims: Gamma-rays escaping the ejecta can be used as a diagnostic tool for studying the characteristics of the explosion. In particular, it is expected that the analysis of the early gamma emission, near the maximum of the optical light curve, could provide information about the distribution of the radioactive elements in the debris. Methods: The gamma data obtained from SN2014J in M 82 by the instruments on board INTEGRAL were analysed paying special attention to the effect that the detailed spectral response has on the measurements of the intensity of the lines. Results: The 158 keV emission of 56Ni has been detected in SN2014J at ~5σ at low energy with both ISGRI and SPI around the maximum of the optical light curve. After correcting the spectral response of the detector, the fluxes in the lines suggest that, in addition to the bulk of radioactive elements buried in the central layers of the debris, there is a plume of 56Ni, with a significance of ~3σ, moving at high velocity and receding from the observer. The mass of the plume is in the range of ~0.03-0.08 M⊙. Conclusions: No SNIa explosion model has ever predicted the mass and geometrical distribution of 56Ni suggested here. According to its optical properties, SN2014J looks like a normal SNIa, so it is extremely important to discern whether it is also representative in the gamma-ray band. Based on observations with INTEGRAL, an ESA project with instruments and the science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, and Spain), the Czech Republic, and Poland and with the participation of Russia and USA.

  3. The Detection of a Light Echo from Type Ia SN 2007af in NGC 5584

    NASA Astrophysics Data System (ADS)

    Drozdov, Dina; Leising, M. D.; Milne, P.; Riess, A. G.

    2013-06-01

    We report the discovery of a light echo (LE) at t ~1000 days past maximum from the normal Type Ia supernova (SNe Ia) SN 2007af in the spiral galaxy NGC 5584. The presence of a LE is supported by photometric data and analysis of the images acquired during the Cepheid campaign using the Hubble Space Telescope (HST) Wide Field Camera 3 (Riess et al. 2011). The F350 and F555 images show a distinct ring-like structure with an additional central source. The images, taken months apart, show an evolution of the ring structure, which is consistent with a growing light echo in time. We find an angular radius of the outer echo to be ~0.29'' - 0.36''. Using the Cepheid distance to NGC 5584 of 24 Mpc, we find the dust illuminated by the light echo to be at a distance ~800 pc from the supernova. This rare discovery adds to the select few light echoes found in Type Ia SNe: SN 1572, SN 1991T, SN 1995E, SN 1998bu, and SN 2006X. Light echoes are powerful tools that probe the environment around supernovae, determine dust properties and characteristics, and could provide constraints on the progenitors, which are not fully understood for SN Ia.

  4. The Kuo-Brown effective interaction: From 18O to the Sn isotopes

    NASA Astrophysics Data System (ADS)

    Engeland, Torgeir; Hjorth-Jensen, Morten; Kartamyshev, Maxim; Osnes, Eivind

    2014-08-01

    After briefly reviewing the pioneering work on effective interactions by Gerry Brown and his group, and the developments which followed, we apply present-day effective interactions to large-scale shell-model calculations on the entire range of Sn isotopes from 102Sn to 132Sn. We have made explorative calculations starting from three different nucleon-nucleon potentials (Argonne V18, CD-Bonn, and N3LO) and evaluated the higher-order contributions to the effective interaction from both G-matrix and Vlowk interactions. Further, we have checked the convergence of intermediate-state excitations up to 10ħω harmonic oscillator energy. Final extensive calculations were made of binding energies, excitation energies and B(E2) transition rates using an effective interaction based on a G-matrix evaluated from the chiral N3LO potential and including intermediate excitations up to 10ħω harmonic oscillator energy. The energy spectra are well reproduced throughout the region while overbinding of the ground states emerges as valence nucleons are added. The B(E2) rates agree well for the heavy isotopes, while they seem too low for the lighter ones.

  5. Quantitative study of coherent pairing modes with two-neutron transfer: Sn isotopes

    NASA Astrophysics Data System (ADS)

    Potel, G.; Idini, A.; Barranco, F.; Vigezzi, E.; Broglia, R. A.

    2013-05-01

    Pairing rotations and pairing vibrations are collective modes associated with a field, the pair field, which changes the number of particles by two. Consequently, they can be studied at profit with the help of two-particle transfer reactions in superfluid and in normal nuclei, respectively. The advent of exotic beams has opened, for the first time, the possibility to carry out such studies in medium heavy nuclei, within the same isotopic chain. The case studied in the present paper is that of the Sn isotopes [essentially from closed (Z=N=50) to closed (Z=50, N=82) shells]. The static and dynamic off-diagonal, long-range order phase coherence in gauge space displayed by pairing rotations and vibrations, respectively, leads to coherent states which behave almost classically. Consequently, these modes are amenable to an accurate nuclear structure description in terms of simple models containing the right physics, in particular, BCS plus quasiparticle random-phase approximation and Hartree-Fock mean field plus random-phase approximation, respectively. The associated two-nucleon transfer spectroscopic amplitudes predicted by such model calculations can thus be viewed as essentially “exact.” This fact, together with the availability of optical potentials for the different real and virtual channels involved in the reactions considered, namely A+2Sn+p, A+1Sn+d, and ASn+t, allows for the calculation of the associated absolute cross sections without, arguably, free parameters. The numerical predictions of the absolute differential cross sections, obtained making use of the above-mentioned nuclear structure and optical potential inputs, within the framework of second-order distorted-wave Born approximation, taking into account simultaneous, successive, and nonorthogonality contributions, provide, within experimental errors in general, and below 10% uncertainty in particular, an overall account of the experimental findings for all of the measured A+2Sn

  6. Magnetic Moments measurement and rare isotope beams: one example ^126Sn

    NASA Astrophysics Data System (ADS)

    Kumbartzki, Gerfried; Benczer-Koller, Noemie

    2012-10-01

    An assessment of the current state of measurements of magnetic moments of ps excited states with low intensity rare isotope beams will be given. ^126Sn was our last experiment before HRIBF/Oak Ridge ceased operation. Results of only a few experiments using the transient field technique and/or recoil in vacuum attenuation have been published. Each experiment posed special challenges and required specific modifications to the setup. The challenges and limitations learned and an outlook for future experiments will be presented.

  7. Late Light Curves of SN 2002cx-like Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Lair, Jessica C.; Kilgore, E. E.; Milne, P.; Bryngelson, G. L.; Leising, M. D.

    2013-01-01

    The use of Type Ia Supernovae (SNe Ia) in cosmological studies as “standard candle” distance indicators lead to the need for a better understanding of these objects. SN 2002cx was a very peculiar SNe Ia that did not fit into any of the known subclasses of SNe Ia and needs to be further understood. We present late-time optical photometry of three more recently discovered objects that have been determined to be SN 2002cx-like Type Ia supernovae: SN 2005hk, SN 2008A, and SN 2008ae. The light curves of these objects show late-time decline rates that are slower than what is seen in normal SNe Ia in the V,R, and I bands, but faster in the B-band.

  8. Visible and Near-infrared Light Curves of SN 2009nr

    NASA Astrophysics Data System (ADS)

    Heath, Jonathan; Bryngelson, Ginger

    2014-03-01

    This study explores the behavior of SN 2009nr, an apparently normal type Ia supernova (SN Ia). A plot of this object's brightness over time is known as a light curve. Because of the uniformity of their light curves, SNe Ia are valuable markers for determining the expansion of the universe and other cosmological parameters. Understanding the properties of these supernovae is vital in order to build our confidence in their use as standard candles. A small, but increasing number of SN Ia late-time observations have been made in the near-infrared (NIR). Most exhibit a flattening of the NIR power even as the visible light declines at a steady rate. It is still unclear as to why they exhibit this behavior and how typical this is. In order to characterize the late behavior of SNe Ia, images of SN 2009nr were analyzed using the Image Reduction and Analysis Facility (IRAF). NIR (J, H, K) images were taken with the 4m Mayall Telescope at Kitt Peak National-Observatory using the FLAMINGOS IR Imaging Spectrometer while visible (B, V, R, I) images used the Mosaic 1 imager. The supernova's apparent magnitude for each night of observation (by filter) was found by using reference stars. We present preliminary light curves of SN 2009nr and a comparison to another SN observed at similar epochs.

  9. The light curve of SN 1987A revisited: constraining production masses of radioactive nuclides

    SciTech Connect

    Seitenzahl, Ivo R.; Timmes, F. X.; Magkotsios, Georgios

    2014-09-01

    We revisit the evidence for the contribution of the long-lived radioactive nuclides {sup 44}Ti, {sup 55}Fe, {sup 56}Co, {sup 57}Co, and {sup 60}Co to the UVOIR light curve of SN 1987A. We show that the V-band luminosity constitutes a roughly constant fraction of the bolometric luminosity between 900 and 1900 days, and we obtain an approximate bolometric light curve out to 4334 days by scaling the late time V-band data by a constant factor where no bolometric light curve data is available. Considering the five most relevant decay chains starting at {sup 44}Ti, {sup 55}Co, {sup 56}Ni, {sup 57}Ni, and {sup 60}Co, we perform a least squares fit to the constructed composite bolometric light curve. For the nickel isotopes, we obtain best fit values of M({sup 56}Ni) = (7.1 ± 0.3) × 10{sup –2} M {sub ☉} and M({sup 57}Ni) = (4.1 ± 1.8) × 10{sup –3} M {sub ☉}. Our best fit {sup 44}Ti mass is M({sup 44}Ti) = (0.55 ± 0.17) × 10{sup –4} M {sub ☉}, which is in disagreement with the much higher (3.1 ± 0.8) × 10{sup –4} M {sub ☉} recently derived from INTEGRAL observations. The associated uncertainties far exceed the best fit values for {sup 55}Co and {sup 60}Co and, as a result, we only give upper limits on the production masses of M({sup 55}Co) < 7.2 × 10{sup –3} M {sub ☉} and M({sup 60}Co) < 1.7 × 10{sup –4} M {sub ☉}. Furthermore, we find that the leptonic channels in the decay of {sup 57}Co (internal conversion and Auger electrons) are a significant contribution and constitute up to 15.5% of the total luminosity. Consideration of the kinetic energy of these electrons is essential in lowering our best fit nickel isotope production ratio to [{sup 57}Ni/{sup 56}Ni] = 2.5 ± 1.1, which is still somewhat high but is in agreement with gamma-ray observations and model predictions.

  10. Production of neutron-rich Ca, Sn, and Xe isotopes in transfer-type reactions with radioactive beams

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Lacroix, D.

    2010-12-15

    The production cross sections of neutron-rich isotopes {sup 52,54,56,58,60}Ca, {sup 136,138,140,142}Sn, and {sup 146,148,150,152}Xe are predicted for future experiments in the diffusive multinucleon transfer reactions {sup 86,90,92,94}Kr, {sup 124,130,132,134}Sn, {sup 136,140,142,146}Xe, and {sup 138,144,146}Ba+{sup 48}Ca with stable and radioactive beams at incident energies close to the Coulomb barrier. Because of the small cross sections, the production of neutron-rich isotopes requires the optimal choice of projectile-target combinations and bombarding energies.

  11. Light stable isotope analysis of meteorites by ion microprobe

    NASA Technical Reports Server (NTRS)

    Mcsween, Harry Y., Jr.

    1994-01-01

    The main goal was to develop the necessary secondary ion mass spectrometer (SIMS) techniques to use a Cameca ims-4f ion microprobe to measure light stable isotope ratios (H, C, O and S) in situ and in non-conducting mineral phases. The intended application of these techniques was the analysis of meteorite samples, although the techniques that have been developed are equally applicable to the investigation of terrestrial samples. The first year established techniques for the analysis of O isotope ratios (delta O-18 and delta O-17) in conducting mineral phases and the measurement of S isotope ratios (delta S-34) in a variety of sulphide phases. In addition, a technique was developed to measure delta S-34 values in sulphates, which are insulators. Other research undertaken in the first year resulted in SIMS techniques for the measurement of wide variety of trace elements in carbonate minerals, with the aim of understanding the nature of alteration fluids in carbonaceous chondrites. In the second year we developed techniques for analyzing O isotope ratios in nonconducting mineral phases. These methods are potentially applicable to the measurement of other light stable isotopes such as H, C and S in insulators. Also, we have further explored the analytical techniques used for the analysis of S isotopes in sulphides by analyzing troilite in a number of L and H ordinary chondrites. This was done to see if there was any systematic differences with petrological type.

  12. Stable light isotope biogeochemistry of hydrothermal systems

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.

    1996-01-01

    The stable isotopic composition of the elements O, H, S and C in minerals and other chemical species can indicate the existence, extent, conditions and the processes (including biological activity) of hydrothermal systems. Hydrothermal alteration of the 18O/16O and D/H values of minerals can be used to detect fossil systems and delineate their areal extent. Water-rock interactions create isotopic signatures which indicate fluid composition, temperature, water-rock ratios, etc. The 18O/16O values of silica and carbonate deposits tend to increase with declining temperature and thus help to map thermal gradients. Measurements of D/H values can help to decipher the origin(s) of hydrothermal fluids. The 34S/32S and 13C/12C values of fluids and minerals reflect the origin of the S and C as well as oxygen fugacities and key redox processes. For example, a wide range of 34S/32S values which are consistent with equilibration below 100 degrees C between sulfide and sulfate can be attributed to sulfur metabolizing bacteria. Depending on its magnitude, the difference in the 13C/12C value of CO2 and carbonates versus organic carbon might be attributed either to equilibrium at hydrothermal temperatures or, if the difference exceeds 1% (10/1000), to organic biosynthesis. Along the thermal gradients of thermal spring outflows, the 13C/12C value of carbonates and 13C-depleted microbial organic carbon increases, principally due to the outgassing of relatively 13C-depleted CO2.

  13. Stable light isotope biogeochemistry of hydrothermal systems.

    PubMed

    Des Marais, D J

    1996-01-01

    The stable isotopic composition of the elements O, H, S and C in minerals and other chemical species can indicate the existence, extent, conditions and the processes (including biological activity) of hydrothermal systems. Hydrothermal alteration of the 18O/16O and D/H values of minerals can be used to detect fossil systems and delineate their areal extent. Water-rock interactions create isotopic signatures which indicate fluid composition, temperature, water-rock ratios, etc. The 18O/16O values of silica and carbonate deposits tend to increase with declining temperature and thus help to map thermal gradients. Measurements of D/H values can help to decipher the origin(s) of hydrothermal fluids. The 34S/32S and 13C/12C values of fluids and minerals reflect the origin of the S and C as well as oxygen fugacities and key redox processes. For example, a wide range of 34S/32S values which are consistent with equilibration below 100 degrees C between sulfide and sulfate can be attributed to sulfur metabolizing bacteria. Depending on its magnitude, the difference in the 13C/12C value of CO2 and carbonates versus organic carbon might be attributed either to equilibrium at hydrothermal temperatures or, if the difference exceeds 1% (10/1000), to organic biosynthesis. Along the thermal gradients of thermal spring outflows, the 13C/12C value of carbonates and 13C-depleted microbial organic carbon increases, principally due to the outgassing of relatively 13C-depleted CO2. PMID:9243011

  14. Mixing of fluids in hydrothermal ore-forming (Sn,W) systems: stable isotope and rare earth elements data

    NASA Astrophysics Data System (ADS)

    Sushchevskaya, T. M.; Popova, J. A.; Velivetskaya, T. A.; Ignatiev, A. V.; Matveeva, S. S.; Limantseva, O. A.

    2012-04-01

    Experimental and physico-chemical modeling data witness to important role of mixing of different type of fluids during tin and tungsten ore formation in hydrothermal systems. Mixing of magmatogeneous fluids, exsolved from granite melts, with exogenic, initially meteoric waters in hydrothermal ore-forming systems may change chemical composition of ore-forming fluid, causing cassiterite and/or wolframite precipitation (Heinrich, 1990; Sushchevskaya, Ryzhenko, 2002). We studied the process of genetically different fluids mixing for two economic Sn-W deposits, situated in the Iultin ore region (North-East of Russia, Chukotka Penninsula). The Iultin and Svetloe deposits are located in the apical parts of close situated leucogranite stocks, formed at the final stage of the Iultin complex emplacement. Both deposits are composed of a series of quartz veins among the flyschoid rocks (T 1-2), cut by the dikes (K1) of lamprophyre, granodiorite porphyre and alpite. The veins of the deposits are dominated by the productive quartz-wolframite-cassiterite-arsenopyrite-muscovite mineral assemblage. Topaz, beryl, fluorite, and albite occur sporadically. The later sulfide (loellingite-stannite-chalcopyrite) and quartz-fluorite-calcite assemblages show insignificant development. The preore quartz veinlets in host hornfels contain disseminated iron sulfides, chalcopyrite, muscovite. Isotopic (H, O, Ar) study of minerals, supplemented by oxygen isotope data of host granites and metamorphic rocks gave us possibility to conclude, that at the Iultin and the Svetloye deposits fluid mixing was fixed on the early stages of deposit formation and could be regarded as probable cause of metal (W, Sn) precipitation. During postore time the intensive involvement of isotopically light exogenic waters have changed: a) the initial character of oxygen isotope zonality; b) the initial hydrogen isotope composition of muscovites, up to meteoric calculated values for productive fluid (while the δ18O

  15. What powers the 3000-day light curve of SN 2006gy?

    NASA Astrophysics Data System (ADS)

    Fox, Ori D.; Smith, Nathan; Ammons, S. Mark; Andrews, Jennifer; Bostroem, K. Azalee; Cenko, S. Bradley; Clayton, Geoffrey C.; Dwek, Eli; Filippenko, Alexei V.; Gallagher, Joseph S.; Kelly, Patrick L.; Mauerhan, Jon C.; Miller, Adam A.; Van Dyk, Schuyler D.

    2015-12-01

    SN 2006gy was the most luminous supernova (SN) ever observed at the time of its discovery and the first of the newly defined class of superluminous supernovae (SLSNe). The extraordinary energetics of SN 2006gy and all SLSNe (>1051 erg) require either atypically large explosion energies (e.g. pair-instability explosion) or the efficient conversion of kinetic into radiative energy (e.g. shock interaction). The mass-loss characteristics can therefore offer important clues regarding the progenitor system. For the case of SN 2006gy, both a scattered and thermal light echo from circumstellar material (CSM) have been reported at later epochs (day ˜800), ruling out the likelihood of a pair-instability event and leading to constraints on the characteristics of the CSM. Owing to the proximity of the SN to the bright host-galaxy nucleus, continued monitoring of the light echo has not been trivial, requiring the high resolution offered by the Hubble Space Telescope (HST) or ground-based adaptive optics (AO). Here, we report detections of SN 2006gy using HST and Keck AO at ˜3000 d post-explosion and consider the emission mechanism for the very late-time light curve. While the optical light curve and optical spectral energy distribution are consistent with a continued scattered-light echo, a thermal echo is insufficient to power the K'-band emission by day 3000. Instead, we present evidence for late-time infrared emission from dust that is radiatively heated by CSM interaction within an extremely dense dust shell, and we consider the implications on the CSM characteristics and progenitor system.

  16. Optimization of thermoelectric efficiency in SnTe: the case for the light band.

    PubMed

    Zhou, Min; Gibbs, Zachary M; Wang, Heng; Han, Yemao; Xin, Caini; Li, Laifeng; Snyder, G Jeffrey

    2014-10-14

    p-Type PbTe is an outstanding high temperature thermoelectric material with zT of 2 at high temperatures due to its complex band structure which leads to high valley degeneracy. Lead-free SnTe has a similar electronic band structure, which suggests that it may also be a good thermoelectric material. However, stoichiometric SnTe is a strongly p-type semiconductor with a carrier concentration of about 1 × 10(20) cm(-3), which corresponds to a minimum Seebeck coefficient and zT. While in the case of p-PbTe (and n-type La3Te4) one would normally achieve higher zT by using high carrier density in order to populate the secondary band with higher valley degeneracy, SnTe behaves differently. It has a very light, upper valence band which is shown in this work to provide higher zT than doping towards the heavier second band. Therefore, decreasing the hole concentration to maximize the performance of the light band results in higher zT than doping into the high degeneracy heavy band. Here we tune the electrical transport properties of SnTe by decreasing the carrier concentration with iodine doping, and increasing the carrier concentration with Gd doping or by making the samples Te deficient. A peak zT value of 0.6 at 700 K was obtained for SnTe0.985I0.015 which optimizes the light, upper valence band, which is about 50% higher than the other peak zT value of 0.4 for GdzSn1-zTe and SnTe1+y which utilize the high valley degeneracy secondary valence band. PMID:25162449

  17. ASYMMETRY IN THE OUTBURST OF SN 1987A DETECTED USING LIGHT ECHO SPECTROSCOPY

    SciTech Connect

    Sinnott, B.; Welch, D. L.; Sutherland, P. G.; Rest, A.; Bergmann, M.

    2013-04-10

    We report direct evidence for asymmetry in the early phases of SN 1987A via optical spectroscopy of five fields of its light echo system. The light echoes allow the first few hundred days of the explosion to be reobserved, with different position angles providing different viewing angles to the supernova. Light echo spectroscopy therefore allows a direct spectroscopic comparison of light originating from different regions of the photosphere during the early phases of SN 1987A. Gemini multi-object spectroscopy of the light echo fields shows fine structure in the H{alpha} line as a smooth function of position angle on the near-circular light echo rings. H{alpha} profiles originating from the northern hemisphere of SN 1987A show an excess in redshifted emission and a blue knee, while southern hemisphere profiles show an excess of blueshifted H{alpha} emission and a red knee. This fine structure is reminiscent of the 'Bochum event' originally observed for SN 1987A, but in an exaggerated form. Maximum deviation from symmetry in the H{alpha} line is observed at position angles 16 Degree-Sign and 186 Degree-Sign , consistent with the major axis of the expanding elongated ejecta. The asymmetry signature observed in the H{alpha} line smoothly diminishes as a function of viewing angle away from the poles of the elongated ejecta. We propose an asymmetric two-sided distribution of {sup 56}Ni most dominant in the southern far quadrant of SN 1987A as the most probable explanation of the observed light echo spectra. This is evidence that the asymmetry of high-velocity {sup 56}Ni in the first few hundred days after explosion is correlated to the geometry of the ejecta some 25 years later.

  18. X-Rays from the Explosion Site: Fifteen Years of Light Curves of SN 1993J

    NASA Technical Reports Server (NTRS)

    Chandra, Poonam; Dwarkadas, Vikram V.; Ray, Alak; Immler, Stefan; Pooley, David

    2009-01-01

    We present a comprehensive analysis of the X-ray light curves of SN 1993J in a nearby galaxy M81. This is the only supernova other than SN 1987A, which is so extensively followed in the X-ray bands. Here we report on SN 1993J observations with the Chandra in the year 2005 and 2008, and Swift observations in 2005, 2006 and 2008. We combined these observations with all available archival data of SN 1993J, which includes ROSAT, ASCA, Chandra, and XMM-Newton, observations from 1993 April to 2006 August. In this paper we report the X-ray light curves of SN 1993J, extending up to fifteen years, in the soft (0.3-2.4 keV), hard (2-8 keV) and combined (0.3-8 keV) bands. The hard and soft-band fluxes decline at different rates initially, but after about 5 years they both undergo a t(sup -1) decline. The soft X-rays, which are initially low, start dominating after a few hundred days. We interpret that most of the emission below 8 keV is coming from the reverse shock which is radiative initially for around first 1000-2000 days and then turn into adiabatic shock. Our hydrodynamic simulation also confirms the reverse shock origin of the observed light curves. We also compare the Ha line luminosity of SN 1993J with its X-ray light curve and note that the Ha line luminosity has a fairly high fraction of the X-ray emission, indicating presence of clumps in the emitting plasma.

  19. Light Echoes and the Progenitor of SN 2016adj in Cen A

    NASA Astrophysics Data System (ADS)

    Sugerman, Ben; Lawrence, Stephen

    2016-02-01

    The Type Ib/IIb supernova (SN) 2016adj is the fifth closest SN to be discovered during the lifetime of HST. This event offers us a rich variety of rare and unique opportunities, including: (1) identifying the progenitor; (2) mapping the three-dimensional structure and chemical composition of the progenitor's circumstellar and the host galaxy's interstellar environments; and (3) testing models of stellar mass loss and high-mass stellar evolution. The progenitor field of the SN has been observed from the near-UV to the mid-IR with HST and Spitzer, which will immediately allow us to accomplish the first science goal by identifying the progenitor (or establishing its upper limits) once new image with the SN present are taken with both observatories. Preliminary analyses of early-time spectra of SN 2016adj indicate its light is being extinguished by at least A(V)=2-4 magnitudes, meaning it is buried deep within the dust lane of Cen A. Echoes of the SN light off of this dust will allow us to produce high-resolution, three-dimensional maps of the structure and composition of the dust in and around the line-of-sight to the SN, which we will use to accomplish science goals (2)-(3) listed above. In particular, we will directly test the hypothesis that Type Ib/IIb SNe come not from very-high mass stars but from only moderately-massive stars that lost their envelopes to close binary companions. Please note that since echoes pass through a given point in space only once, data are permanently lost for each epoch that is not observed. While we will propose for continued observations in the Cycle 13 call for proposals, most of the science we propose cannot be achieved if the observations in this proposal are not taken before Cycle 13 begins.

  20. SPECTROPOLARIMETRY OF THE TYPE Ia SN 2007sr TWO MONTHS AFTER MAXIMUM LIGHT

    SciTech Connect

    Zelaya, P.; Quinn, J. R.; Clocchiatti, A.; Baade, D.; Patat, F.; Hoeflich, P.; Maund, J.; Wang, L.; Wheeler, J. C.

    2013-02-01

    We present late-time spectropolarimetric observations of SN 2007sr, obtained with the Very Large Telescope at the ESO Paranal Observatory when the object was 63 days after maximum light. The late-time spectrum displays strong line polarization in the Ca II absorption features. SN 2007sr adds to the case of some normal Type Ia supernovae that show high line polarization or repolarization at late times, a fact that might be connected with the presence of high-velocity features at early times.

  1. Shell-model states with seniority ν =3 , 5, and 7 in odd-A neutron-rich Sn isotopes

    NASA Astrophysics Data System (ADS)

    Iskra, Ł. W.; Broda, R.; Janssens, R. V. F.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Wrzesiński, J.; Zhu, S.

    2016-01-01

    Excited states with seniority ν =3 , 5, and 7 have been investigated in odd neutron-rich 119,121,123,125Sn isotopes produced by fusion-fission of 6.9-MeV/A 48Ca beams with 208Pb and 238U targets and by fission of a 238U target bombarded with 6.7-MeV/A 64Ni beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known 27 /2- isomers were expanded by identifying new deexcitation paths feeding 23 /2+ long-lived states and 21 /2+ levels. Competing branches in the decay of 23 /2- states toward two 19 /2- levels were delineated as well. In 119Sn, a new 23 /2+ isomer was identified, while a similar 23 /2+ long-lived state, proposed earlier in 121Sn, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of ν =3 excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the 27 /2- isomers, an elaborate structure of negative-parity levels was established reaching the (39 /2- ), ν =7 states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity (35 /2+ ), (31 /2+ ), and (27 /2+ ) states were established, feeding the 23 /2+ isomers via cascades of three transitions. In the ,123Sn121 isotopes, these sequences also enabled the delineation of higher-lying levels, up to (43 /2+ ) states. In 123Sn, a short half-life was determined for the (35 /2+ ) state. Shell-model calculations were carried out for all the odd Sn isotopes, from 129Sn down to 119

  2. Detection of a Light Echo from the Otherwise Normal SN 2007af

    NASA Astrophysics Data System (ADS)

    Drozdov, D.; Leising, M. D.; Milne, P. A.; Pearcy, J.; Riess, A. G.; Macri, L. M.; Bryngelson, G. L.; Garnavich, P. M.

    2015-05-01

    We present the discovery of a light echo from SN 2007af, a normal Type Ia supernova (SN Ia) in NGC 5584. Hubble Space Telescope images taken three years post explosion reveal two separate echoes: an outer echo and an extended central region, which we propose to be an inner echo for which details are unresolved. Multiple images were obtained in the F160W, F350LP, F555W, and F814W using the Wide Field Camera 3. If the outer echo is produced by an interstellar dust sheet perpendicular to the line of sight, it is located ∼800 pc in front of the SN. The dust for the inner echo is 0.45 pc \\lt d\\lt 90 pc away from the SN. The inner echo color is consistent with typical interstellar dust wavelength-dependent scattering cross-sections, while the outer echo is redder than predicted. Both dust sheets, if in the foreground, are optically thin for scattering, and the outer echo sheet thickness is consistent with the inferred extinction from peak brightness. Whether the inner echo is from interstellar or circumstellar dust is ambiguous. Overall, the echo characteristics are quite similar to previously observed SN Ia echoes.

  3. Scattered-Light Echoes from the Historical Galactic Supernovae Cassiopeia A and Tycho (SN 1572)

    SciTech Connect

    Rest, A; Welch, D L; Suntzeff, N B; Oaster, L; Lanning, H; Olsen, K; Smith, R C; Becker, A C; Bergmann, M; Challis, P; Clocchiatti, A; Cook, K H; Damke, G; Garg, A; Huber, M E; Matheson, T; Minniti, D; Prieto, J L; Wood-Vasey, W M

    2008-05-06

    We report the discovery of an extensive system of scattered light echo arclets associated with the recent supernovae in the local neighborhood of the Milky Way: Tycho (SN 1572) and Cassiopeia A. Existing work suggests that the Tycho SN was a thermonuclear explosion while the Cas A supernova was a core collapse explosion. Precise classifications according to modern nomenclature require spectra of the outburst light. In the case of ancient SNe, this can only be done with spectroscopy of their light echo, where the discovery of the light echoes from the outburst light is the first step. Adjacent light echo positions suggest that Cas A and Tycho may share common scattering dust structures. If so, it is possible to measure precise distances between historical Galactic supernovae. On-going surveys that alert on the development of bright scattered-light echo features have the potential to reveal detailed spectroscopic information for many recent Galactic supernovae, both directly visible and obscured by dust in the Galactic plane.

  4. ZnO:SnO nanorods and nanosheets and their enhanced photocatalytic activity under visible light irradiation

    SciTech Connect

    Harish, S. E-mail: suruponnus@gmail.com; Ponnusamy, S. E-mail: suruponnus@gmail.com; Muthamizhchelvan, C.; Silambarasan, A.; Navaneethan, M.; Archana, J.; Hayakawa, Y.

    2015-06-24

    ZnO-SnO nanocomposites were synthesized by a simple hydrothermal method. It was found that Sn concentration acted as a crucial factor in determining the morphology of ZnO-SnO nanostructures, in the presence of ethylenediamine (EDA) as a stabilizing agent. XRD analysis confirmed the formation of ZnO and SnO with good crystallinity. The morphological analysis revealed tin oxide (SnO) nanoparticles coated on the surface of ZnO nanorods and nanosheets. The photocatalytic activity of synthesized samples were evaluated by methylene blue (MB) as a model pollutant under visible light irradiation. Photocatalysis studies revealed that, ZnO-SnO nanocomposites show the enhanced photocatalytic activity compared to ZnO, which could be attributed to the formation of hetero-junction between ZnO and SnO of MB degradation. Sn concentration can extend the light absorption spectra of ZnO to visible light region and enhance the visible light photocatalytic activity. This research could provide new insights to the development of excellent photocatalyst with efficient performance for pollution control.

  5. SALT spectroscopic classification of PS15bqc as a type-IIb SN before maximum light

    NASA Astrophysics Data System (ADS)

    Jha, S. W.; Pan, Y.-C.; Foley, R. J.; Rest, A.; Scolnic, D.; Smith, K. W.; Wright, D.; Smartt, S. J.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Miszalski, B.

    2015-08-01

    We obtained SALT (+RSS) spectroscopy of PS15bqc on 2015 Aug 10.8 UT, covering the wavelength range 340-920 nm. Cross-correlation of the spectrum with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows PS15bqc is likely a type-IIb supernova a few days before maximum light, with good matches to spectra of SN 1993J at -3 or -2 days from maximum.

  6. Low mass SN Ia and the late light curve

    SciTech Connect

    Colgate, S.A.; Fryer, C.L.; Hand, K.P.

    1995-12-31

    The late bolometric light curves of type Ia supernovae, when measured accurately over several years, show an exponential decay with a 56d half-life over a drop in luminosity of 8 magnitudes (10 half-lives). The late-time light curve is thought to be governed by the decay of Co{sup 56}, whose 77d half-life must then be modified to account for the observed decay time. Two mechanisms, both relying upon the positron fraction of the Co{sup 56} decay, have been proposed to explain this modification. One explanation requires a large amount of emission at infra-red wavelengths where it would not be detected. The other explanation has proposed a progressive transparency or leakage of the high energy positrons (Colgate, Petschek and Kriese, 1980). For the positrons to leak out of the expanding nebula at the required rate necessary to produce the modified 56d exponential, the mass of the ejecta from a one foe (10{sup 51} erg in kinetic energy) explosion must be small, M{sub ejec} = 0.4M{sub {circle_dot}} with M{sub ejec} {proportional_to} KE{sup 0.5}. Thus, in this leakage explanation, any reasonable estimate of the total energy of the explosion requires that the ejected mass be very much less than the Chandrasekhar mass of 1.4M{sub {circle_dot}}. This is very difficult to explain with the ``canonical`` Chandrasekhar-mass thermonuclear explosion that disintegrates the original white dwarf star. This result leads us to pursue alternate mechanisms of type Ia supernovae. These mechanisms include sub-Chandrasekhar thermonuclear explosions and the accretion induced collapse of Chandrasekhar mass white dwarfs. We will summarize the advantages and disadvantages of both mechanisms with considerable detail spent on our new accretion induced collapse simulations. These mechanisms lead to lower Ni{sup 56} production and hence result in type Ia supernovae with luminosities decreased down to {approximately} 50% that predicted by the ``standard`` model.

  7. Isotope effects in photo dissociation of ozone with visible light

    NASA Astrophysics Data System (ADS)

    Früchtl, Marion; Janssen, Christof; Röckmann, Thomas

    2014-05-01

    Ozone (O3) plays a key role for many chemical oxidation processes in the Earth's atmosphere. In these chemical reactions, ozone can transfer oxygen to other trace gases. This is particularly interesting, since O3 has a very peculiar isotope composition. Following the mass dependent fractionation equation δ17O = 0.52 * δ18O, most fractionation processes depend directly on mass. However, O3 shows an offset to the mass dependent fractionation line. Processes, which show such anomalies, are termed mass independent fractionations (MIF). A very well studied example for a chemical reaction that leads to mass independent fractionation is the O3 formation reaction. To what degree O3 destruction reactions need to be considered in order to understand the isotope composition of atmospheric O3 is still not fully understood and an open question within scientific community. We set up new experiments to investigate the isotope effect resulting from photo dissociation of O3 in the Chappuis band (R1). Initial O3 is produced by an electric discharge. After photolysis O3 is collected in a cold trap at the triple point temperature of nitrogen (63K). O3 is then converted to O2 in order to measure the oxygen isotopes of O3 using isotope ratio mass spectrometry. To isolate O3 photo dissociation (R1) from O3 decomposition (R2) and secondary O3 formation (R3), we use varying amounts of carbon monoxide (CO) as O atom quencher (R4). In this way we suppress the O + O3 reaction (R3) and determine the isotope fractionation in R1 and R2 separately. We present first results on the isotope effects in O3 photo dissociation with visible light in the presence of different bath gases. Results are interpreted based on chemical kinetics modeling. (R1) O3 + hυ → O (3P) + O2 (R2) O3 + O (3P) → 2 O2 (R3) O + O2 + M → O3 + M (R4) O (3P) + CO + M → CO2 + M

  8. Microwave assisted synthesis of porous ZnO/SnS heterojunction and its application in visible light degradation of ciprofloxacin

    NASA Astrophysics Data System (ADS)

    Makama, A. B.; Salmiaton, A.; Saion, E. B.; Choong, T. S. Y.; Abdullah, N.

    2016-07-01

    Porous ZnO/SnS heterojunctions were successfully synthesized via microwave-assisted heating of aqueous solutions containing different amounts of SnS precursors (SnCl2 and Na2S) in the presence of fixed amount of ZnCO3 nanoparticles. The experimental results revealed that the heterojunctions exhibited much higher visible light-driven photocatalytic activity for the degradation of the ciprofloxacin than pure SnS nanocrystals. The photocatalytic degradation efficiency (1-Ct/C0) of the pollutant for the most active heterogeneous nanostructure is about four times more efficient than pure SnS. The enhanced photocatalytic efficiency is ascribed to the synergic effect of high photon absorption and reduction in the recombination of electrons and holes because of efficient separation and electron transfer from the SnS to ZnO nanoparticles.

  9. Rotating Type Ia SN progenitors: explosion and light curves

    SciTech Connect

    Dominguez, I.; Piersanti, L.; Gagliardi, S.; Straniero, O.; Tornambe, A.; Bravo, E.

    2005-10-21

    High redshift SNe Ia have been recently used to calibrate the cosmological distance scale and to infer the existence of the dark energy. The reliability of such a method depends on the effective knowledge of the absolute brightness of this class of supernovae. This would require a complete understanding of the physics of SNeIa.Starting from an accreting rotating white dwarf, the only progenitor that we found to be able to grow till the Chandrasekhar mass and undergo a thermonuclear explosion, we simulate the explosion, deriving the nucleosynthesis and the light curve. We explore the final outcome in the framework of a 1D delayed detonation model, where the characteristic density for which the transition from deflagration to detonation takes place is a free parameter.Although preliminary, our results imply that rotating white dwarfs produce a range of explosive conditions, characterized by different ignition densities and total masses. Maximum luminosities of successfully explosive models differ up to 0.11 mag. In a few cases, the formation of a small highly neutronised remnant is found.

  10. Direct bandgap GeSn light emitting diodes for short-wave infrared applications grown on Si

    NASA Astrophysics Data System (ADS)

    von den Driesch, Nils; Stange, Daniela; Wirths, Stephan; Rainko, Denis; Mussler, Gregor; Stoica, Toma; Ikonic, Zoran; Hartmann, Jean-Michel; Grützmacher, Detlev; Mantl, Siegfried; Buca, Dan

    2016-03-01

    The experimental demonstration of fundamental direct bandgap, group IV GeSn alloys has constituted an important step towards realization of the last missing ingredient for electronic-photonic integrated circuits, i.e. the efficient group IV laser source. In this contribution, we present electroluminescence studies of reduced-pressure CVD grown, direct bandgap GeSn light emitting diodes (LEDs) with Sn contents up to 11 at.%. Besides homojunction GeSn LEDs, complex heterojunction structures, such as GeSn/Ge multi quantum wells (MQWs) have been studied. Structural and compositional investigations confirm high crystalline quality, abrupt interfaces and tailored strain of the grown structures. While also being suitable for light absorption applications, all devices show light emission in a narrow short-wave infrared (SWIR) range. Temperature dependent electroluminescence (EL) clearly indicates a fundamentally direct bandgap in the 11 at.% Sn sample, with room temperature emission at around 0.55 eV (2.25 µm). We have, however, identified some limitations of the GeSn/Ge MQW approach regarding emission efficiency, which can be overcome by introducing SiGeSn ternary alloys as quantum confinement barriers.

  11. Chandra Observations of SN 1987A: The Soft X-Ray Light Curve Revisited

    NASA Technical Reports Server (NTRS)

    Helder, E. A.; Broos, P. S.; Dewey, D.; Dwek, E.; McCray, R.; Park, S.; Racusin, J. L.; Zhekov, S. A.; Burrows, D. N.

    2013-01-01

    We report on the present stage of SN 1987A as observed by the Chandra X-Ray Observatory. We reanalyze published Chandra observations and add three more epochs of Chandra data to get a consistent picture of the evolution of the X-ray fluxes in several energy bands. We discuss the implications of several calibration issues for Chandra data. Using the most recent Chandra calibration files, we find that the 0.5-2.0 keV band fluxes of SN 1987A have increased by approximately 6 x 10(exp-13) erg s(exp-1)cm(exp-2) per year since 2009. This is in contrast with our previous result that the 0.5-2.0 keV light curve showed a sudden flattening in 2009. Based on our new analysis, we conclude that the forward shock is still in full interaction with the equatorial ring.

  12. Using SN 1987A light echoes to determine mass loss from the progenitor

    NASA Technical Reports Server (NTRS)

    Crotts, Arlin P. S.; Kunkel, William E.

    1991-01-01

    The hypothesis that the blue progenitor of SN 1987A passed through a blue supergiant phase ending with the expulsion of the outer envelope is tested. The many light echoes seen near SN 1987A were used to search for a mass flow from the progenitor and for abrupt density changes at the limits of this smooth mass flow. The progenitor needed roughly a million yr to create these structures, assuming a constant mass loss at 15 km/s. The dust in the region is small-grained and isotropically scattering. Interaction between the progenitor blue supergiant and red supergiant winds is probably contained within a roughly spherical structure 1.5 pc in diameter.

  13. CHANDRA OBSERVATIONS OF SN 1987A: THE SOFT X-RAY LIGHT CURVE REVISITED

    SciTech Connect

    Helder, E. A.; Broos, P. S.; Burrows, D. N.; Dewey, D.; Dwek, E.; McCray, R.; Park, S.; Racusin, J. L.; Zhekov, S. A.

    2013-02-10

    We report on the present stage of SN 1987A as observed by the Chandra X-Ray Observatory. We reanalyze published Chandra observations and add three more epochs of Chandra data to get a consistent picture of the evolution of the X-ray fluxes in several energy bands. We discuss the implications of several calibration issues for Chandra data. Using the most recent Chandra calibration files, we find that the 0.5-2.0 keV band fluxes of SN 1987A have increased by {approx}6 Multiplication-Sign 10{sup -13} erg s{sup -1} cm{sup -2} per year since 2009. This is in contrast with our previous result that the 0.5-2.0 keV light curve showed a sudden flattening in 2009. Based on our new analysis, we conclude that the forward shock is still in full interaction with the equatorial ring.

  14. Constraints on the Origin of the First Light from SN 2014J

    NASA Astrophysics Data System (ADS)

    Goobar, A.; Kromer, M.; Siverd, R.; Stassun, K. G.; Pepper, J.; Amanullah, R.; Kasliwal, M.; Sollerman, J.; Taddia, F.

    2015-01-01

    We study the very early light curve of supernova 2014J (SN 2014J) using the high-cadence broad-band imaging data obtained by the Kilodegree Extremely Little Telescope, which fortuitously observed M 82 around the time of the explosion, starting more than 2 months prior to detection, with up to 20 observations per night. These observations are complemented by observations in two narrow-band filters used in an Hα survey of nearby galaxies by the intermediate Palomar Transient Factory that also captured the first days of the brightening of the supernova. The evolution of the light curves is consistent with the expected signal from the cooling of shock heated material of large scale dimensions, gsim1R ⊙. This could be due to heated material of the progenitor, a companion star or pre-existing circumstellar environment, e.g., in the form of an accretion disk. Structure seen in the light curves during the first days after explosion could also originate from radioactive material in the outer parts of an exploding white dwarf, as suggested from the early detection of gamma-rays. The model degeneracy translates into a systematic uncertainty of ±0.3 days on the estimate of the first light from SN 2014J.

  15. Early-Time Flux Measurements of SN 2014J Obtained with Small Robotic Telescopes: Extending the AAVSO Light Curve

    NASA Astrophysics Data System (ADS)

    Poppe, B.; Plaggenborg, T.; Zheng, W.; Shivvers, I.; Itagaki, K.; Filippenko, A. V.; Kunz, J.

    2015-06-01

    In this work, early-time photometry of supernova (SN) 2014J is presented, extending the AAVSO CCD database to prediscovery dates. The applicability of NASA's small robotic MicroObservatory Network telescopes for photometric measurements is evaluated. Prediscovery and postdiscovery photometry of SN 2014J is measured from images taken by two different telescopes of the network, and is compared to measurements from the Katzman Automatic Imaging Telescope and the Itagaki Observatory. In the early light-curve phase (which exhibits stable spectral behavior with constant color indices), these data agree with reasonably high accuracy (better than 0.05 mag around maximum brightness, and 0.15 mag at earlier times). Owing to the changing spectral energy distribution of the SN and the different spectral characteristics of the systems used, differences increase after maximum light. We augment light curves of SN 2014J downloaded from the American Association of Variable Star Observers (AAVSO) online database with these data, and consider the complete brightness evolution of this important Type Ia SN. Furthermore, the first detection presented here (Jan. 15.427, 2014) appears to be one of the earliest observations of SN 2014J yet published, taken less than a day after the SN exploded.

  16. Collectivity in the light xenon isotopes: A shell model study

    SciTech Connect

    Caurier, E.; Nowacki, F.; Sieja, K.; Poves, A.

    2010-12-15

    The lightest xenon isotopes are studied in the shell model framework, within a valence space that comprises all the orbits lying between the magic closures N=Z=50 and N=Z=82. The calculations produce collective deformed structures of triaxial nature that encompass nicely the known experimental data. Predictions are made for the (still unknown) N=Z nucleus {sup 108}Xe. The results are interpreted in terms of the competition between the quadrupole correlations enhanced by the pseudo-SU(3) structure of the positive parity orbits and the pairing correlations brought in by the 0h{sub 11/2} orbit. We also have studied the effect of the excitations from the {sup 100}Sn core on our predictions. We show that the backbending in this region is due to the alignment of two particles in the 0h{sub 11/2} orbit. In the N=Z case, one neutron and one proton align to J=11 and T=0. In {sup 110,112}Xe the alignment begins in the J=10, T=1 channel and it is dominantly of neutron-neutron type. Approaching the band termination the alignment of a neutron-proton pair to J=11 and T=0 takes over. In a more academic mood, we have studied the role of the isovector and isoscalar pairing correlations on the structure on the yrast bands of {sup 108,110}Xe and examined the possible existence of isovector and isoscalar pairing condensates in these N{approx}{approx}Z nuclei.

  17. A light curve and its analysis of Type Ia SN 1604

    NASA Astrophysics Data System (ADS)

    Lee, Eun Hee; Lee, Dae-Young; Mihn, Byeong-Hee

    2015-08-01

    SN 1604, known as Kepler’s supernova, was first detected by European observers, but a full light curve including its peak brightness and initial decline part can only be completed by extra data from Korean royal astronomers of four centuries ago. Nowadays, it is considered one of the Type Ia galactic supernovae, which show the empirical correlation between decline rate and peak luminosity - so called Phillips relation or width-luminosity (W-L) relation. Here, we reconstruct a new light curve based on both the Korean and European records of SN 1604. Using this light curve and W-L relation, we present an observed rise time and decline rates after peak, and derive its absolute peak magnitude and distance. In this study, observed rise time (≈ 19±1 days) shows a good agreement with typical mean time of Type Ia SNe, while the initial decline rates such as Δm15(V) and Δm20(V) represent steeper and faster values than the extra-galactic SNe Ia. Moreover, its absolute peak magnitude and distance derived from the W-L relation show much fainter and nearer values, respectively than the estimated results by different methods

  18. Si based mid-infrared GeSn photo detectors and light emitters

    NASA Astrophysics Data System (ADS)

    Du, Wei; Pham, Thach; Margetis, Joe; Tran, Huong; Ghetmiri, Seyed A.; Mosleh, Aboozar; Sun, Greg; Soref, Richard A.; Tolle, John; Naseem, Hameed A.; Li, Baohua; Yu, Shui-Qing

    2015-08-01

    In this work, high performance GeSn photoconductor and light emitting diodes (LED) have been demonstrated. For the photoconductor, the high responsivity was achieved due to high photoconductive gain, which is attributed to the novel optical and electrical design. The longwave cutoff at 2.4 μm was also observed at room temperature. For LED, temperature-dependent study was conducted. The electroluminescence (EL) spectra at different temperatures were obtained and EL peak shift was observed. Moreover, the emission power at different temperatures was measured. High power emission at 2.1 μm was achieved.

  19. Temperature-dependent electroluminescence from GeSn heterojunction light-emitting diode on Si substrate

    NASA Astrophysics Data System (ADS)

    Chang, Chiao; Li, Hui; Huang, Ssu-Hsuan; Lin, Li-Chien; Cheng, Hung-Hsiang

    2016-04-01

    The electroluminescence from a Ge/GeSn/Ge p-i-n light-emitting diode on Si was investigated under different temperatures ranging from 25 to 150 K. The diode was operated at a low injection current density of 13 A/cm2. We obtained no-phonon- and phonon-assisted replicas in emission spectra. Also, the relationship between indirect bandgap energy and temperature was investigated. The temperature-dependent bandgap energy followed Varshni’s empirical expression with α = 4.884 × 10-4 eV/K and β = 130 K.

  20. Morphology controlled synthesis of SnS₂ nanomaterial for promoting photocatalytic reduction of aqueous Cr(VI) under visible light.

    PubMed

    Mondal, Chanchal; Ganguly, Mainak; Pal, Jaya; Roy, Anindita; Jana, Jayasmita; Pal, Tarasankar

    2014-04-15

    A mild, template free protocol has been demonstrated for SnS2 nanoflake formation at the gram level from SnCl2 and thioacetamide (TAA). The SnS2 nanoflakes congregate to nanoflowers and nanoyarns with variable TAA concentrations. BET measurements reveal that the synthesized nanomaterials are highly porous having very high surface area, and the nanoflower has higher surface area than the nanoyarn. The synthesized nanomaterial finds application for promoting photoreduction of extremely toxic and lethal Cr(VI) under visible light irradiation due to their porous nature. The nanoflowers photocatalyst is proved to be superior to nanoyarn due to the increased surface area and higher pore volume. It was also inferred that increased pH decreased the reaction rate. The present result suggests that the morphology-dependent photoreduction of Cr(VI) by SnS2 nanomaterial under visible light exposure will endorse a new technique for harvesting energy and purification of wastewater. PMID:24649847

  1. Nucleon-pair states of even-even Sn isotopes based on realistic effective interactions

    NASA Astrophysics Data System (ADS)

    Cheng, Y. Y.; Qi, C.; Zhao, Y. M.; Arima, A.

    2016-08-01

    In this paper we study yrast states of 128,126,124Sn and 104,106,108Sn by using the monopole-optimized realistic interactions in terms of both the shell model (SM) and the nucleon-pair approximation (NPA). For yrast states of 128,126Sn and 104,106Sn, we calculate the overlaps between the wave functions obtained in the full SM space and those obtained in the truncated NPA space, and find that most of these overlaps are very close to 1. Very interestingly, for most of these states with positive parity and even spin or with negative parity and odd spin, the SM wave function is found to be well represented by one nucleon-pair basis state, viz., a simple picture of "nucleon-pair states" (nucleon-pair configuration without mixings) emerges. In 128,126Sn, the positive-parity (or negative-parity) yrast states with spin J >10 (or J >7 ) are found to be well described by breaking one or two S pairs in the 101+ (or 71-) state, i.e., the yrast state of seniority-two, spin-maximum, and positive-parity (or negative-parity), into non-S pair(s). Similar regularity is also pointed out for 104,106Sn. The evolution of E 2 transition rates between low-lying states in 128,126,124Sn is discussed in terms of the seniority scheme.

  2. Asymmetries in SN 2014J near Maximum Light Revealed through Spectropolarimetry

    NASA Astrophysics Data System (ADS)

    Porter, Amber L.; Leising, Mark D.; Williams, G. Grant; Milne, Peter; Smith, Paul; Smith, Nathan; Bilinski, Christopher; Hoffman, Jennifer L.; Huk, Leah; Leonard, Douglas C.

    2016-09-01

    We present spectropolarimetric observations of the nearby Type Ia supernova SN 2014J in M82 over six epochs: +0, +7, +23, +51, +77, +109, and +111 days with respect to B-band maximum. The strong continuum polarization, which is constant with time, shows a wavelength dependence unlike that produced by linear dichroism in Milky Way dust. The observed polarization may be due entirely to interstellar dust or include a circumstellar scattering component. We find that the polarization angle aligns with the magnetic field of the host galaxy, arguing for an interstellar origin. Additionally, we confirm a peak in polarization at short wavelengths that would imply {R}V\\lt 2 along the light of sight, in agreement with earlier polarization measurements. For illustrative purposes, we include a two-component fit to the continuum polarization of our +51-day epoch that combines a circumstellar scattering component with interstellar dust where scattering can account for over half of the polarization at 4000 Å. Upon removal of the interstellar polarization signal, SN 2014J exhibits very low levels of continuum polarization. Asymmetries in the distribution of elements within the ejecta are visible through moderate levels of time-variable polarization in accordance with the Si ii λ6355 absorption line. At maximum light, the line polarization reaches ∼0.6% and decreases to ∼ 0.4 % 1 week later. This feature also forms a loop on the {q}{RSP}{--}{u}{RSP} plane, illustrating that the ion does not have an axisymmetric distribution. The observed polarization properties suggest that the explosion geometry of SN 2014J is generally spheroidal with a clumpy distribution of silicon.

  3. Asymmetries in SN 2014J near Maximum Light Revealed through Spectropolarimetry

    NASA Astrophysics Data System (ADS)

    Porter, Amber L.; Leising, Mark D.; Williams, G. Grant; Milne, Peter; Smith, Paul; Smith, Nathan; Bilinski, Christopher; Hoffman, Jennifer L.; Huk, Leah; Leonard, Douglas C.

    2016-09-01

    We present spectropolarimetric observations of the nearby Type Ia supernova SN 2014J in M82 over six epochs: +0, +7, +23, +51, +77, +109, and +111 days with respect to B-band maximum. The strong continuum polarization, which is constant with time, shows a wavelength dependence unlike that produced by linear dichroism in Milky Way dust. The observed polarization may be due entirely to interstellar dust or include a circumstellar scattering component. We find that the polarization angle aligns with the magnetic field of the host galaxy, arguing for an interstellar origin. Additionally, we confirm a peak in polarization at short wavelengths that would imply {R}V\\lt 2 along the light of sight, in agreement with earlier polarization measurements. For illustrative purposes, we include a two-component fit to the continuum polarization of our +51-day epoch that combines a circumstellar scattering component with interstellar dust where scattering can account for over half of the polarization at 4000 Å. Upon removal of the interstellar polarization signal, SN 2014J exhibits very low levels of continuum polarization. Asymmetries in the distribution of elements within the ejecta are visible through moderate levels of time-variable polarization in accordance with the Si ii λ6355 absorption line. At maximum light, the line polarization reaches ˜0.6% and decreases to ˜ 0.4 % 1 week later. This feature also forms a loop on the {q}{RSP}{--}{u}{RSP} plane, illustrating that the ion does not have an axisymmetric distribution. The observed polarization properties suggest that the explosion geometry of SN 2014J is generally spheroidal with a clumpy distribution of silicon.

  4. Level densities and γ-ray strength functions in Sn isotopes

    NASA Astrophysics Data System (ADS)

    Toft, H. K.; Larsen, A. C.; Agvaanluvsan, U.; Bürger, A.; Guttormsen, M.; Mitchell, G. E.; Nyhus, H. T.; Schiller, A.; Siem, S.; Syed, N. U. H.; Voinov, A.

    2010-06-01

    The nuclear level densities of Sn118,119 and the γ-ray strength functions of Sn116,118,119 below the neutron separation energy are extracted with the Oslo method using the (He3,αγ) and (He3,He3'γ) reactions. The level-density function of Sn119 displays steplike structures. The microcanonical entropies are deduced from the level densities, and the single neutron entropy of Sn119 is determined to be 1.7 ± 0.2 kB. Results from a combinatorial model support the interpretation that some of the low-energy steps in the level density function are caused by neutron pair breaking. An enhancement in all the γ-ray strength functions of Sn116-119, compared to standard models for radiative strength, is observed for the γ-ray energy region of ≃4-11 MeV. These small resonances all have a centroid energy of 8.0(1) MeV and an integrated strength corresponding to 1.7(9)% of the classical Thomas-Reiche-Kuhn sum rule. The Sn resonances may be due to electric dipole neutron skin oscillations or to an enhancement of the giant magnetic dipole resonance.

  5. Final Report on Isotope Ratio Techniques for Light Water Reactors

    SciTech Connect

    Gerlach, David C.; Gesh, Christopher J.; Hurley, David E.; Mitchell, Mark R.; Meriwether, George H.; Reid, Bruce D.

    2009-07-01

    The Isotope Ratio Method (IRM) is a technique for estimating the energy or plutonium production in a fission reactor by measuring isotope ratios in non-fuel reactor components. The isotope ratios in these components can then be directly related to the cumulative energy production with standard reactor modeling methods.

  6. Rare-isotope and kinetic studies of Pt/SnO2 catalysts

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T.; Wood, George M.; Schryer, David R.; Hess, Robert V.; Miller, Irvin M.; Kielin, Erik J.

    1990-01-01

    Closed-cycle pulsed CO2 laser operation requires the use of an efficient CO-O2 recombination catalyst for these dissociation products which otherwise would degrade the laser operation. The catalyst must not only operate at low temperatures but also must operate efficiently for long periods. In the case of the Laser Atmospheric Wind Sounder (LAWS) laser, an operational lifetime of 3 years is required. Additionally, in order to minimize atmospheric absorption and enhance aerosol scatter of laser radiation, the LAWS system will operate at 9.1 micrometers with an oxygen-18 isotope CO2 lasing medium. Consequently, the catalyst must not only operate at low temperatures but must also preserve the isotopic integrity of the rare-isotope composition in the recombination mode. Several years ago an investigation of commercially available and newly synthesized recombination catalysts for use in closed-cycle pulsed common and rare-isotope CO2 lasers was implemented at the NASA Langley Research Center. Since that time, mechanistic efforts utilizing both common and rare oxygen isotopes have been implemented and continue. Rare-isotope studies utilizing commercially available platinum-tin oxide catalyst have demonstrated that the catalyst contributes oxygen-16 to the product carbon dioxide thus rendering it unusable for rare-isotope applications. A technique has been developed for modification of the surface of the common-isotope catalyst to render it usable. Results of kinetic and isotope label studies using plug flow, recycle plug flow, and closed internal recycle plug flow reactor configuration modes are discussed.

  7. Preliminary NIR Late Light Curve of the Type Ia Supernova SN2009nr

    NASA Astrophysics Data System (ADS)

    Heath, Jonathan; Bryngelson, G.

    2013-01-01

    Type Ia supernovae (SNe Ia) are important in determining the expansion of the universe based on the uniformity of their light curves. It is essential to understand the behavior of these supernovae in order to strengthen our confidence in their use as standard candles. A small, but increasing number of SNe Ia have been observed later than the 200 day epoch in the near-infrared (NIR). Most of these exhibit a flattening of the NIR power, even as the visible light declines at a steady rate. It is unclear as to exactly what causes this behavior, and how typical it is. In order to characterize the late behavior of SNe Ia, images of the supernova SN2009nr were analyzed using the Image Reduction and Analysis Facility (IRAF). These images were taken with the 4m Mayall Telescope at Kitt Peak National-Observatory using the FLAMINGOS IR Imaging Spectrometer. The supernova’s magnitude was normalized with respect to the magnitudes of known stars so that traits related to the supernova may be compared to others. We present preliminary NIR (J, H, K) light curves of the observed supernova and compare them to other SNe Ia observed at these epochs.

  8. Microwave fabrication of Cu2ZnSnS4 nanoparticle and its visible light photocatalytic properties

    PubMed Central

    2014-01-01

    Cu2ZnSnS4 nanoparticle with an average diameter of approximately 31 nm has been successfully synthesized by a time effective microwave fabrication method. The crystal structure, surface morphology, and microstructure of the Cu2ZnSnS4 nanoparticle were characterized. Moreover, the visible light photocatalytic ability of the Cu2ZnSnS4 nanoparticle toward degradation of methylene blue (MB) was also studied. About 30% of MB was degraded after 240 min irradiation when employing Cu2ZnSnS4 nanoparticle as a photocatalyst. However, almost all MB was decomposed after 90 min irradiation when introducing a small amount of H2O2 as a co-photocatalyst. The enhancement of the photocatalytic performance was attributed to the synergetic effect between the Cu2ZnSnS4 nanoparticle and H2O2. The detailed photocatalytic degradation mechanism of MB by the Cu2ZnSnS4 was further proposed. PMID:25237289

  9. SALT spectroscopic classification of PS16atu (SN 2016atv) as a type-Ia supernova after maximum light

    NASA Astrophysics Data System (ADS)

    Jha, S. W.; Pan, Y.-C.; Foley, R. J.; Rest, A.; Scolnic, D.; Kotze, M.

    2016-03-01

    We obtained SALT (+RSS) spectroscopy of PS16atu (SN 2016atv) on 2016 Mar 10.1 UT, covering the wavelength range 350-920 nm. Cross-correlation of the spectrum with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows PS16atu is a type-Ia supernova approximately a week past maximum light.

  10. Synthesis, characterization and photocatalytic properties of SnO2-ZnO composite under UV-A light

    NASA Astrophysics Data System (ADS)

    Kuzhalosai, V.; Subash, B.; Senthilraja, A.; Dhatshanamurthi, P.; Shanthi, M.

    2013-11-01

    The SnO2 loaded ZnO (SnO2-ZnO) was successfully synthesized by precipitation-decomposition method. The catalyst was characterized by X-ray diffraction (XRD), high resolution scanning electron microscope (HR-SEM) images, energy dispersive spectrum (EDS), diffuse reflectance spectra (DRS), photoluminescence spectra (PL) and BET surface area measurements. The photocatalytic activity of SnO2-ZnO was investigated for the degradation of Acid Orange 10 (AO 10) in aqueous solution using UV-A light. SnO2-ZnO is found to be more efficient than commercial ZnO, bare ZnO, TiO2-P25 and TiO2 (Merck) at pH 12 for the mineralization of AO 10 dye. The effects of operational parameters such as the amount of photocatalyst, dye concentration, initial pH on photo mineralization of AO 10 dye have been analyzed. The mineralization of AO 10 has been confirmed by chemical oxygen demand (COD) measurements. A degradation mechanism is proposed for the degradation of AO 10 with SnO2-ZnO under UV-A light. This catalyst is found to be reusable.

  11. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    NASA Astrophysics Data System (ADS)

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application.

  12. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation.

    PubMed

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as (3)He/(4)He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as (3)He/(4)He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high (3)He/(4)He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application. PMID:26813491

  13. Highly Efficient Quantum Sieving in Porous Graphene-like Carbon Nitride for Light Isotopes Separation

    PubMed Central

    Qu, Yuanyuan; Li, Feng; Zhou, Hongcai; Zhao, Mingwen

    2016-01-01

    Light isotopes separation, such as 3He/4He, H2/D2, H2/T2, etc., is crucial for various advanced technologies including isotope labeling, nuclear weapons, cryogenics and power generation. However, their nearly identical chemical properties made the separation challenging. The low productivity of the present isotopes separation approaches hinders the relevant applications. An efficient membrane with high performance for isotopes separation is quite appealing. Based on first-principles calculations, we theoretically demonstrated that highly efficient light isotopes separation, such as 3He/4He, can be reached in a porous graphene-like carbon nitride material via quantum sieving effect. Under moderate tensile strain, the quantum sieving of the carbon nitride membrane can be effectively tuned in a continuous way, leading to a temperature window with high 3He/4He selectivity and permeance acceptable for efficient isotopes harvest in industrial application. This mechanism also holds for separation of other light isotopes, such as H2/D2, H2/T2. Such tunable quantum sieving opens a promising avenue for light isotopes separation for industrial application. PMID:26813491

  14. Si based GeSn light emitter: mid-infrared devices in Si photonics

    NASA Astrophysics Data System (ADS)

    Yu, S. Q.; Ghetmiri, S. A.; Du, W.; Margetis, J.; Zhou, Y.; Mosleh, A.; Al-Kabi, S.; Nazzal, A.; Sun, G.; Soref, R. A.; Tolle, J.; Li, B.; Naseem, H. A.

    2015-02-01

    Ge1-xSnx/Ge thin films and Ge/Ge1-xSnx/Ge n-i-p double heterostructure (DHS) have been grown using commercially available reduced pressure chemical vapor deposition (RPCVD) reactor. The Sn compositional material and optical characteristics have been investigated. A direct bandgap GeSn material has been identified with Sn composition of 10%. The GeSn DHS samples were fabricated into LED devices. Room temperature electroluminescence spectra were studied. A maximum emission power of 28mW was obtained with 10% Sn LED under the injection current density of 800 A/cm2.

  15. Near-infrared light absorption by polycrystalline SiSn alloys grown on insulating layers

    SciTech Connect

    Kurosawa, Masashi; Kato, Motohiro; Yamaha, Takashi; Taoka, Noriyuki; Nakatsuka, Osamu; Zaima, Shigeaki

    2015-04-27

    High-Sn-content SiSn alloys are strongly desired for the next-generation near-infrared optoelectronics. A polycrystalline growth study has been conducted on amorphous SiSn layers with a Sn-content of 2%–30% deposited on either a substrate of SiO{sub 2} or SiN. Incorporating 30% Sn into Si permits the crystallization of the amorphous layers at annealing temperatures below the melting point of Sn (231.9 °C). Composition analyses indicate that approximately 20% of the Sn atoms are substituted into the Si lattice after solid-phase crystallization at 150–220 °C for 5 h. Correspondingly, the optical absorption edge is red-shifted from 1.12 eV (Si) to 0.83 eV (Si{sub 1−x}Sn{sub x} (x ≈ 0.18 ± 0.04)), and the difference between the indirect and direct band gap is significantly reduced from 3.1 eV (Si) to 0.22 eV (Si{sub 1−x}Sn{sub x} (x ≈ 0.18 ± 0.04)). These results suggest that with higher substitutional Sn content the SiSn alloys could become a direct band-gap material, which would provide benefits for Si photonics.

  16. The Very Early Light Curve of SN 2015F in NGC 2442: A Possible Detection of Shock-heated Cooling Emission and Constraints on SN Ia Progenitor System

    NASA Astrophysics Data System (ADS)

    Im, Myungshin; Choi, Changsu; Yoon, Sung-Chul; Kim, Jae-Woo; Ehgamberdiev, Shuhrat A.; Monard, Libert A. G.; Sung, Hyun-Il

    2015-11-01

    The main progenitor candidates of Type Ia supernovae (SNe Ia) are white dwarfs in binary systems where the companion star is another white dwarf (double degenerate (DD) system) or a less-evolved, non-degenerate star with R* ≳ 0.1 R⊙ (single degenerate system). However, no direct observational evidence exists to tell us which progenitor system is more common. Recent studies suggest that the light curve of a supernova shortly after its explosion can be used to set a limit on the progenitor size, R*. Here, we report high-cadence monitoring observations of SN 2015F, a normal SN Ia in the galaxy NGC 2442, starting about 84 days before the first light time. Using our daily cadence data, we capture the emergence of the radioactively powered light curve; more importantly, with >97.4% confidence, we detect possible dim precursor emission that appears roughly 1.5 days before the rise of the radioactively powered emission. The signal is consistent with theoretical expectations for a progenitor system involving a companion star with R* ≃ 0.1-1 R⊙ or a prompt explosion of a DD system, but is inconsistent with the typically invoked size of a white dwarf progenitor of R* ˜ 0.01 R⊙. Upper limits on the precursor emission also constrain the progenitor size to be R* ≲ 0.1 R⊙ with a companion star size of R* ≲ 1.0 R⊙, excluding a very large companion star in the progenitor system. Additionally, we find that the distance to SN 2015F is 23.9 ± 0.4 Mpc.

  17. Progenitors of Type IIB Supernovae in the Light of Radio and X-Rays from SN 2013DF

    NASA Astrophysics Data System (ADS)

    Kamble, Atish; Margutti, Raffaella; Soderberg, Alicia M.; Chakraborti, Sayan; Fransson, Claes; Chevalier, Roger; Powell, Diana; Milisavljevic, Dan; Parrent, Jerod; Bietenholz, Michael

    2016-02-01

    We present radio and X-ray observations of the nearby SN IIb 2013df in NGC 4414 from 10 to 250 days after the explosion. The radio emission showed a peculiar steep-to-shallow spectral evolution. We present a model in which inverse Compton cooling of synchrotron emitting electrons can account for the observed spectral and light curve evolution. A significant mass-loss rate, \\dot{M}≈ 8× {10}-5 {M}⊙ yr-1 for a wind velocity of 10 km s-1, is estimated from the detailed modeling of radio and X-ray emission, which are primarily due to synchrotron and bremsstrahlung, respectively. We show that SN 2013df is similar to SN 1993J in various ways. The shock wave speed of SN 2013df was found to be average among the radio supernovae; {v}{sh}/c˜ 0.07. We did not find any significant deviation from smooth decline in the light curve of SN 2013df. One of the main results of our self-consistent multiband modeling is the significant deviation from energy equipartition between magnetic fields and relativistic electrons behind the shock. We estimate {ɛ }e=200{ɛ }B. In general for SNe IIb, we find that the presence of bright optical cooling envelope emission is linked with free-free radio absorption and bright thermal X-ray emission. This finding suggests that more extended progenitors, similar to that of SN 2013df, suffer from substantial mass loss in the years before the supernova.

  18. Role of Sn in the Regeneration of Pt/γ-Al2O3 Light Alkane Dehydrogenation Catalysts

    PubMed Central

    2016-01-01

    Alumina-supported Pt is one of the major industrial catalysts for light alkane dehydrogenation. This catalyst loses activity during reaction, with coke formation often considered as the reason for deactivation. As we show in this study, the amount and nature of carbon deposits do not directly correlate with the loss of activity. Rather, it is the transformation of subnanometer Pt species into larger Pt nanoparticles that appears to be responsible for the loss of catalytic activity. Surprisingly, a portion of the Sn remains atomically dispersed on the alumina surface in the spent catalyst and helps in the redispersion of the Pt. In the absence of Sn on the alumina support, the larger Pt nanoparticles formed during reaction are not redispersed during oxidative regeneration. It is known that Sn is added as a promoter in the industrial catalyst to help in achieving high propene selectivity and to minimize coke formation. This work shows that an important role of Sn is to help in the regeneration of Pt, by providing nucleation sites on the alumina surface. Aberration-corrected scanning transmission electron microscopy helps to provide unique insights into the operating characteristics of an industrially important catalyst by demonstrating the role of promoter elements, such as Sn, in the oxidative regeneration of Pt on γ-Al2O3. PMID:27076991

  19. Systematic study of GeSn heterostructure-based light-emitting diodes towards mid-infrared applications

    NASA Astrophysics Data System (ADS)

    Zhou, Yiyin; Dou, Wei; Du, Wei; Pham, Thach; Ghetmiri, Seyed Amir; Al-Kabi, Sattar; Mosleh, Aboozar; Alher, Murtadha; Margetis, Joe; Tolle, John; Sun, Greg; Soref, Richard; Li, Baohua; Mortazavi, Mansour; Naseem, Hameed; Yu, Shui-Qing

    2016-07-01

    Temperature-dependent characteristics of GeSn light-emitting diodes with Sn composition up to 9.2% have been systematically studied. Such diodes were based on Ge/GeSn/Ge double heterostructures (DHS) that were grown directly on a Si substrate via a chemical vapor deposition system. Both photoluminescence and electroluminescence spectra have been characterized at temperatures from 300 to 77 K. Based on our theoretical calculation, all GeSn alloys in this study are indirect bandgap materials. However, due to the small energy separation between direct and indirect bandgap, and the fact that radiative recombination rate greater than non-radiative, the emissions are mainly from the direct Γ-valley to valence band transitions. The electroluminescence emissions under current injection levels from 102 to 357 A/cm2 were investigated at 300 K. The monotonic increase of the integrated electroluminescence intensity was observed for each sample. Moreover, the electronic band structures of the DHS were discussed. Despite the indirect GeSn bandgap owing to the compressive strain, type-I band alignment was achieved with the barrier heights ranging from 11 to 47 meV.

  20. Evidence for rapid variability in the optical light curve of the Type Ia SN 2014J⋆

    NASA Astrophysics Data System (ADS)

    Bonanos, A. Z.; Boumis, P.

    2016-01-01

    We present results of high-cadence monitoring of the optical light curve of the nearby, Type Ia SN 2014J in M 82, using the 2.3 m Aristarchos telescope. B and V-band photometry on days 15-18 after tmax(B) was obtained with a cadence of 2 min per band, revealing evidence for rapid variability at the 0.02-0.05 mag level on timescales of 15-60 min on all four nights. The decline slope was measured as steeper in the B-band than in the V-band, and to steadily decrease in both bands from 0.15 mag day-1 (night 1) to 0.04 mag day-1 (night 4) in V, and from 0.19 mag day-1 (night 1) to 0.06 mag day-1 (night 4) in B, corresponding to the onset of the secondary maximum. We propose that rapid variability could be due to one or a combination of the following scenarios: the clumpiness of the ejecta, their interaction with circumstellar material, the asymmetry of the explosion, or the mechanism causing the secondary maximum in the near-infrared light curve. We encourage the community to undertake high-cadence monitoring of future, nearby and bright supernovae to investigate the intraday behaviour of their light curves. Based on observations made with the 2.3 m Aristarchos telescope, Helmos Observatory, Greece, which is operated by the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Greece.Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A19

  1. Observation of heavy- and light-hole split direct bandgap photoluminescence from tensile-strained GeSn (0.03% Sn)

    NASA Astrophysics Data System (ADS)

    Harris, Thomas R.; Yeo, Yung Kee; Ryu, Mee-Yi; Beeler, Richard T.; Kouvetakis, John

    2014-09-01

    Temperature- (T-) and laser power-dependent photoluminescence (PL) measurements have been made for the tensile-strained, undoped GeSn (0.03% Sn) film grown on Si substrate. The PL results show not only clear strain-split direct bandgap transitions to the light-hole (LH) and heavy-hole (HH) bands at energies of 0.827 and 0.851 eV at 10 K, respectively, but also clearly show both strong direct and indirect bandgap related PL emissions at almost all temperatures, which are rarely observed. This split of PL emissions can be directly observed only at low T and moderate laser power, and the two PL peaks merge into one broad PL peak at room temperature, which is mainly due to the HH PL emission rather than LH transition. The evolution of T-dependent PL results also clearly show the competitive nature between the direct and indirect bandgap related PL transitions as T changes. The PL analysis also indicates that the energy gap reduction in Γ valley could be larger, whereas the bandgap reduction in L valley could be smaller than the theory predicted. As a result, the separation energy between Γ and L valleys (˜86 meV at 300 K) is smaller than theory predicted (125 meV) for this Ge-like sample, which is mainly due to the tensile strain. This finding strongly suggests that the indirect-to-direct bandgap transition of Ge1-ySny could be achieved at much lower Sn concentration than originally anticipated if one utilizes the tensile strain properly. Thus, Ge1-ySny alloys could be attractive materials for the fabrication of direct bandgap Si-based light emitting devices.

  2. Developing Potential New Reference Materials for Light Isotopes in Foodstuffs

    NASA Astrophysics Data System (ADS)

    Frew, Russell; Van Hale, Robert; Clarke, Dianne; Abrahim, Aiman; Resch, Christian; Mayr, Leopold; Cannavan, Andrew; Gröning, Manfred

    2013-04-01

    Measurements of subtle variations in stable isotope ratios provide the means for verifying food integrity in numerous ways. Adulterants usually have different isotopic composition so their presence in a food is readily detectable. Stable isotope measurements can also be used to determine the region of production of the food. In most cases the ability of stable isotope measurements to verify, or otherwise reject, the authenticity of the food is greatly enhanced by comparison of a result to a reference database. The more high-quality data in the database, the more statistical power is afforded by the comparison. A serious weakness at present is the lack of reference materials in food matrices available to the community. Thus researchers have to rely on in-house standards for calibration and quality assurance. The result is that there are numerous datasets published that may be internally consistent but it is exceedingly difficult to combine these datasets into a cohesive database. This is particularly important for measurements of the hydrogen isotopes. Here we present a survey of the stable isotope (^2H, ^13C and ^15N) composition of 12 Reference Materials from the International Atomic Energy Agency catalogue. All but one of these materials are plant matter and have been developed as reference materials for other applications such as radionuclide or trace element measurements. Thus they have been verified as suitable materials in terms of stability and homogeneity for those tests. The purpose of this work is to ascertain if they are similarly suitable as stable isotope reference materials. The results from our survey show that there is a wide range in elemental and isotopic composition among these materials. For example, the ^15N values range from-13.5‰ to +18.6‰ and the nitrogen elemental composition range is from 0.7% to 9.7%. The ^13C values range from -20‰ to -40‰ and the carbon elemental composition ranges from 15% to 47%. We are now in the process of

  3. SALT spectroscopic classification of PS16efm (= SN 2016fxu) as a type-Ic supernova after maximum light

    NASA Astrophysics Data System (ADS)

    Jha, S. W.; Dettman, K.; Pan, Y.-C.; Foley, R. J.; Rest, A.; Scolnic, D.; Kotze, M.

    2016-09-01

    We obtained SALT (+RSS) spectroscopy of PS16efm (= SN 2016fxu) on 2016 Sep 8.0 UT, covering the wavelength range 350-920 nm. Cross-correlation of the spectrum with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows PS16efm is a type-Ic supernova approximately two to three weeks past maximum light.

  4. Efficient photocatalytic reduction of aqueous Cr(VI) over flower-like SnIn4S8 microspheres under visible light illumination.

    PubMed

    Wang, Lin; Li, Xinyong; Teng, Wei; Zhao, Qidong; Shi, Yong; Yue, Renliang; Chen, Yunfa

    2013-01-15

    Photocatalytic reduction of aqueous Cr(VI) was successfully achieved on nanostructured SnIn(4)S(8). The SnIn(4)S(8) particles with flower-like nanostructure were synthesized via a facile solvothermal method. UV-vis diffuse reflectance spectra (DRS) indicated that the SnIn(4)S(8) particles had strong absorption in visible region and the band gap was estimated to be from 2.27 to 2.35 eV. The photocatalytic reduction of aqueous Cr(VI) by flower-like SnIn(4)S(8) was evaluated under visible light (λ>400 nm) irradiation. The polyvinyl pyrrolidone (PVP) assisted SnIn(4)S(8) sample exhibits excellent removal efficiency of Cr(VI) (~97%) and good photocatalytic stability. The predominant photocatalytic activity is due to its large surface area, strong absorption in visible-light region and excellent charge separation characteristics. PMID:23177248

  5. Late-time spectroscopy of SN 2002hh: a continued visible light echo with no shock interaction yet

    NASA Astrophysics Data System (ADS)

    Andrews, J. E.; Smith, Nathan; Mauerhan, Jon C.

    2015-08-01

    Supernova (SN) 2002hh was unusual among core-collapse SNe because it was highly reddened, and displayed a bright infrared (IR) excess due to radiatively heated dust in its circumstellar medium (CSM). Estimates for the mass of dust responsible for the IR echo suggested the presence of a massive shell within 0.26 pc of the star. For a velocity of 5000-10 000 km s-1, this material should be hit by the SN blast wave at late times, starting at roughly 12 years post-explosion. We have obtained deep late-time spectra with the Multiple Mirror Telescope (MMT) Blue Channel spectrograph to search for any spectral signatures of ongoing shock interaction. Interaction with a strength comparable to SN 1987A's collision with the equatorial ring would be detected in our data. However, in the spectra reported here, we do not detect clear signs of strong CSM interaction, contrary to expectations based on the reported radii of the dust shell. We do, however, detect emission associated with the old SN, and we find that the broad lines in the spectrum indicate a continuation of an ongoing reflected light echo, which appears similar to the spectrum at peak luminosity for this Type II-P event.

  6. Discovery of a Scattered-Light Echo around SN 2016adj

    NASA Astrophysics Data System (ADS)

    Sugerman, Ben; Lawrence, Stephen

    2016-04-01

    SN 2016adj was imaged with the Hubble Space Telescope (HST) WFC3 UVIS camera on UT 2016 Mar 19.97-20.10 as part of DD-14487 (P.I. Sugerman). A four-point sub-pixel dither pattern was used to image the SN in F438W, F547M, and F814W with total exposure times of 1400 s, 1600 s, and 1320 s, respectively.

  7. Band Gap Tunable Zn2SnO4 Nanocubes through Thermal Effect and Their Outstanding Ultraviolet Light Photoresponse

    PubMed Central

    Zhao, Yan; Hu, Linfeng; Liu, Hui; Liao, Meiyong; Fang, Xiaosheng; Wu, Limin

    2014-01-01

    This work presents a method for synthesis of high-yield, uniform and band gap tunable Zn2SnO4 nanocubes. These nanocubes can be further self-assembled into a series of novel nanofilms with tunable optical band gaps from 3.54 to 3.18 eV by simply increasing the heat treatment temperature. The Zn2SnO4 nanocube-nanofilm based device has been successfully fabricated and presents obviously higher photocurrent, larger photocurrent to dark current ratio than the previously reported individual nanostructure-based UV-light photodetectors, and could be used in high performance photodetectors, solar cells, and electrode materials for Li-ion battery. PMID:25355096

  8. A manual for a Laboratory Information Management System (LIMS) for light stable isotopes

    USGS Publications Warehouse

    Coplen, Tyler B.

    1998-01-01

    The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program is presented herein. Major benefits of this system include (i) an increase in laboratory efficiency, (ii) reduction in the use of paper, (iii) reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) decreased errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for stable isotope laboratories. Since the original publication of the manual for LIMS for Light Stable Isotopes, the isotopes 3 H, 3 He, and 14 C, and the chlorofluorocarbons (CFCs), CFC-11, CFC-12, and CFC-113, have been added to this program.

  9. A manual for a laboratory information management system (LIMS) for light stable isotopes

    USGS Publications Warehouse

    Coplen, Tyler B.

    1997-01-01

    The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program is presented herein. Major benefits of this system include (i) an increase in laboratory efficiency, (ii) reduction in the use of paper, (iii) reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) decreased errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for stable isotope laboratories. Since the original publication of the manual for LIMS for Light Stable Isotopes, the isotopes 3 H, 3 He, and 14 C, and the chlorofluorocarbons (CFCs), CFC-11, CFC-12, and CFC-113, have been added to this program.

  10. Thermal treatment synthesis of SnO2 nanoparticles and investigation of its light harvesting application

    NASA Astrophysics Data System (ADS)

    Dadkhah, Mahnaz; Ansari, Fatemeh; Salavati-Niasari, Masoud

    2016-07-01

    In this research, nanostructured SnO2 materials have been prepared via thermal treatment method with the aid of new Schiff base complex. N, N'-bis(salicylidene)-1,2-propylenediamine (H2salpn) has been used as Schiff base to prepare a new Schiff base complex. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and TEM. Then, as-prepared SnO2 nanoparticles have been applied as working electrode in dye-sensitized solar cells sensitizing with two different natural dyes: madder and mignonette.

  11. Effect of photosynthetic light dosage on carbon isotope composition in the coral skeleton: Long-term culture of Porites spp.

    NASA Astrophysics Data System (ADS)

    Omata, Tamano; Suzuki, Atsushi; Sato, Takanori; Minoshima, Kayo; Nomaru, Eriko; Murakami, Akio; Murayama, Shohei; Kawahata, Hodaka; Maruyama, Tadashi

    2008-06-01

    Whereas the oxygen isotope ratio of the coral skeleton is used for reconstruction of past information on seawater, the carbon isotope ratio is considered a proxy for physiological processes, principally photosynthesis and respiration. However, the fractionation of carbon isotopes in biogenic carbonate such as coral skeleton is still unclear. We conducted a long-term culture experiment of Porites spp. corals at different light dosages (light intensity, 100, 300, or 500 μmol m-2 s-1; daily light period, 10 or 12 h) at 25 ± 0.6°C to examine the contribution of photosynthetic activity to skeletal carbon isotope composition. Corals were grown in sand-filtered seawater and not fed; thus, they subsisted from photosynthesis of symbiotic algae. As the daily dose of photosynthetically active radiation increased, the rate of annual extension also increased. Mean isotope compositions shifted; the carbon isotope compositions (δ13C) became heavier and the oxygen isotope compositions (δ18O) became lighter at higher radiation dose. Skeletal δ18O decrease coincided with increasing skeletal growth rate, indicating the influence of so-called kinetic isotope effects. The observed δ13C increase should be subject to both kinetic and metabolic isotope effects, with the latter reflecting skeletal δ13C enrichment due to photosynthesis by symbiotic algae. Using a vector approach in the δ13C-δ18O plane, we discriminated between kinetic and metabolic isotope effects on δ13C. The calculated δ13C changes from metabolic isotope effects were light dose dependent. The δ13C fractionation curve related to metabolic isotope effects is very similar to the photosynthesis-irradiance curve, indicating the direct contribution of photosynthetic activity to metabolic isotope effects. In contrast, δ13C fractionation related to kinetic isotope effects gradually increased as the growth rate increased. Our experiment demonstrated that the kinetic and metabolic isotope effects in coral skeleton

  12. Carbon isotope fractionation between Fe-carbide and diamond; a light C isotope reservoir in the deep Earth and Core?

    NASA Astrophysics Data System (ADS)

    Mikhail, S.; Jones, A. P.; Hunt, S. A.; Guillermier, C.; Dobson, D. P.; Tomlinson, E.; Dan, H.; Milledge, H.; Franchi, I.; Wood, I.; Beard, A.; Verchovsky, S.

    2010-12-01

    The largest accessible reservoir for terrestrial carbon is the mantle; however the core may yield even more. Carbon is commonly proposed as the light element (or one of) to make up the observed density deficit in the earth’s metallic core (NAKAJIMA et al., 2009). The potential isotopic effects of carbon incorporation into the core have not yet been investigated. In-situ ion probe (nanoSIMS) mapping and imaging of carbon isotope variations across rare sub-mm-scale Fe-rich carbide inclusions in mantle diamond (from Jagersfontein, South Africa) show the carbide to be significantly depleted in 13C relative to their diamond host. Distinctive textures suggest metallic liquid precipitates similar in geometry to (giant) nitrogen platelets, controlled by the octahedral symmetry of diamond, which we interpret as syngenic formation. The difference in δ13C values between the two natural phases for diamond-Fe carbide, gives an isotopic fractionation factor (ΔC) which agrees well with HPHT multi-anvil experiments (5-9 GPa and >1400°C). Our measured ΔC between Fe-carbide and diamond may only have local significance, but the measured isotopic values represent characterization of the highest PT carbide known (i.e. > minimum depth of the diamond stability field ≈ 150 km). The direction and magnitude of ΔC agrees with observations of the ΔC between cohenite-graphite in iron meteorites (DEINES and WICKMAN, 1975) and both agree with HPHT experiments, thus suggesting that carbon in the deep Earth, and particularly in the core, may be similarly fractionated (i.e. depleted in the 13C). Since metallic liquid drained from the silicate mantle to form the core during the early Earth, we can use our values as a proxy to constrain evolution of deep carbon reservoirs such as the core and bulk silicate Earth. For example, we can test the suggestion of Grady et al (2004) that the upper mantle value of δ13C ≈ -5 ‰ may not be representative of the bulk Earth, since solar system

  13. Synthesis of scaly Sn3O4/TiO2 nanobelt heterostructures for enhanced UV-visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Chen, Guohui; Ji, Shaozheng; Sang, Yuanhua; Chang, Sujie; Wang, Yana; Hao, Pin; Claverie, Jerome; Liu, Hong; Yu, Guangwei

    2015-02-01

    A novel scaly Sn3O4/TiO2 nanobelt heterostructured photocatalyst was fabricated via a facile hydrothermal route. The scaly Sn3O4 nanoflakes can be synthesized in situ and assembled on surface coarsened TiO2 nanobelts through a hydrothermal process. The morphology and distribution of Sn3O4 nanoflakes can be well-controlled by simply tuning the Sn/Ti molar ratio of the reactants. Compared with single phase nanostructures of Sn3O4 and TiO2, the scaly hybrid nanobelts exhibited markedly enhanced photoelectrochemical (PEC) response, which caused higher photocatalytic hydrogen evolution even without the assistance of Pt as a co-catalyst, and enhanced the degradation ability of organic pollutants under both UV and visible light irradiation. In addition to the increased exposure of active facets and broad light absorption, the outstanding performance is ascribed to the matching energy band structure between Sn3O4 and TiO2 at the two sides of the heterostructure, which efficiently reduces the recombination of photo-excited electron-hole pairs and prolongs the lifetime of charge carriers. Both photocatalytic assessment and PEC tests revealed that Sn3O4/TiO2 heterostructures with a molar ratio of Sn/Ti of 2/1 exhibited the highest photocatalytic activity. This study provides a facile and low-cost method for the large scale production of Sn3O4 based materials in various applications.A novel scaly Sn3O4/TiO2 nanobelt heterostructured photocatalyst was fabricated via a facile hydrothermal route. The scaly Sn3O4 nanoflakes can be synthesized in situ and assembled on surface coarsened TiO2 nanobelts through a hydrothermal process. The morphology and distribution of Sn3O4 nanoflakes can be well-controlled by simply tuning the Sn/Ti molar ratio of the reactants. Compared with single phase nanostructures of Sn3O4 and TiO2, the scaly hybrid nanobelts exhibited markedly enhanced photoelectrochemical (PEC) response, which caused higher photocatalytic hydrogen evolution even without the

  14. Evolution of isotopic composition of reprocessed uranium during the multiple recycling in light water reactors with natural uranium feed

    SciTech Connect

    Smirnov, A. Yu. Sulaberidze, G. A.; Alekseev, P. N.; Dudnikov, A. A.; Nevinitsa, V. A. Proselkov, V. N.; Chibinyaev, A. V.

    2012-12-15

    A complex approach based on the consistent modeling of neutron-physics processes and processes of cascade separation of isotopes is applied for analyzing physical problems of the multiple usage of reprocessed uranium in the fuel cycle of light water reactors. A number of scenarios of multiple recycling of reprocessed uranium in light water reactors are considered. In the process, an excess absorption of neutrons by the {sup 236}U isotope is compensated by re-enrichment in the {sup 235}U isotope. Specific consumptions of natural uranium for re-enrichment of the reprocessed uranium depending on the content of the {sup 232}U isotope are obtained.

  15. Mass-independent fractionation of mercury isotopes in compact fluorescent light bulbs

    NASA Astrophysics Data System (ADS)

    Mead, C.; Anbar, A. D.; Lyons, J. R.; Johnson, T. M.

    2010-12-01

    Compact fluorescent lightbulbs (CFLs) are a growing source of Hg pollution. The high-energy environment of the CFLs combined with the known partitioning of Hg into the bulb walls could provide an environment for unusual isotope fractionation that could be used to trace pollution from improper bulb disposal. To investigate this possibility, we analyzed the isotope composition of Hg in CFL glass, phosphor powder, and whole bulbs from CFLs of known ages. We observed large, mass-independent fractionation of Hg isotopes between Hg embedded in the bulb wall and Hg in the liquid and vapor phases, which are the initial reservoir of Hg in the bulb. This fractionation results in the bulb wall showing enrichment of 198Hg, 199Hg, 200Hg, 201Hg, and 204Hg relative to 202Hg, the most abundant isotope. Both the amount of Hg embedded in the glass and the magnitude of the isotope enrichment were found to increase with the number of hours of light bulb use. For a CFL used for 3600 hours (with a rated lifetime of 10,000 hours), the isotopic composition of the Hg in the glass was enriched by 34.5‰, 4.1‰, 6.3‰, 21.1‰, and 12.1‰ for 198Hg/202Hg, 199Hg/202Hg, 200Hg/202Hg, 201Hg/202Hg, and 204Hg/202Hg, respectively, compared to NIST SRM-3133. This pattern of isotope enrichments is not correlated with mass differences for any of the isotope ratios. In contrast, the other mass-independent effects that have recently been observed in Hg isotopes (i.e., the nuclear volume and magnetic isotope effects) resemble mass-dependent fractionation for the even mass isotopes and are anomalous only for the odd mass isotopes, 199Hg and 201Hg. First order theoretical calculations using Hg absorption and emission data for each of the hyperfine components of the 253.7 nm line have shown that similar fractionation can be produced through an optical self-shielding effect. This effect occurs because each Hg isotope has a different degree of optical saturation at their respective absorption wavelength

  16. Ge{sub 1−x−y}Si{sub x}Sn{sub y} light emitting diodes on silicon for mid-infrared photonic applications

    SciTech Connect

    Gallagher, J. D.; Xu, C.; Menéndez, J.; Senaratne, C. L.; Wallace, P. M.; Kouvetakis, J.; Aoki, T.

    2015-10-07

    This paper reports initial the demonstration of prototype Ge{sub 1−x−y}Si{sub x}Sn{sub y} light emitting diodes with distinct direct and indirect edges and high quality I-V characteristics. The devices are fabricated on Si (100) wafers in heterostructure pin geometry [n-Ge/i-Ge{sub 1−x−y}Si{sub x}Sn{sub y}/p-Ge(Sn/Si)] using ultra low-temperature (T < 300 °C) depositions of the highly reactive chemical sources Si{sub 4}H{sub 10}, Ge{sub 4}H{sub 10}, Ge{sub 3}H{sub 8}, and SnD{sub 4}. The Sn content in the i-Ge{sub 1−x−y}Si{sub x}Sn{sub y} layer was varied from ∼3.5% to 11%, while the Si content was kept constant near 3%. The Si/Sn amounts in the p-layer were selected to mitigate the lattice mismatch so that the top interface grows defect-free, thereby reducing the deleterious effects of mismatch-induced dislocations on the optical/electrical properties. The spectral responsivity plots of the devices reveal sharp and well-defined absorption edges that systematically red-shift in the mid-IR from 1750 to 2100 nm with increasing Sn content from 3.5% to 11%. The electroluminescence spectra reveal strong direct-gap emission peaks and weak lower energy shoulders attributed to indirect gaps. Both peaks in a given spectrum red-shift with increasing Sn content and their separation decreases as the material approaches direct gap conditions in analogy with binary Ge{sub 1−y}Sn{sub y} counterparts. These findings-combined with the enhanced thermal stability of Ge{sub 1−x−y}Si{sub x}Sn{sub y} relative to Ge{sub 1−y}Sn{sub y} and the observation that ternary alloy disorder does not adversely affect the emission properties—indicate that Ge{sub 1−x−y}Si{sub x}Sn{sub y} may represent a practical target system for future generations of group-IV light sources on Si.

  17. VizieR Online Data Catalog: BVRI light curves of 3 SN (Munari+, 2013)

    NASA Astrophysics Data System (ADS)

    Munari, U.; Henden, A.; Belligoli, R.; Castellani, F.; Cherini, G.; Righetti, G. L.; Vagnozzi, A.

    2015-03-01

    BVRcIc photometry of the three program supernovae was obtained with several robotic, remotely or manually controlled telescopes operated by ANS Collaboration. Technical details of this network of telescopes running since 2005, their operational procedures and sample results are presented by Munari et al. (2012BaltA..21...13M). Detailed analysis of the photometric performances and measurements of the actual transmission profiles for all the photometric filter sets in use is presented by Munari and Moretti (2012BaltA..21...13M). Additional BVRcIc measurements of SN 2011fe and SN 2012aw were obtained at the Astrokolkhoz Observatory in New Mexico with K35, a 35cm remotely operated telescope which houses a set of Astrodon BVRcIc multi-layer dielectric filters. (4 data files).

  18. VizieR Online Data Catalog: SN 2011fu BVRI light curves (Kumar+, 2013)

    NASA Astrophysics Data System (ADS)

    Kumar, B.; Pandey, S. B.; Sahu, D. K.; Vinko, J.; Moskvitin, A. S.; Anupama, G. C.; Bhatt, V. K.; Ordasi, A.; Nagy, A.; Sokolov, V. V.; Sokolova, T. N.; Komarova, V. N.; Kumar, B.; Bose, S.; Roy, R.; Sagar, R.

    2014-05-01

    SN 2011fu was discovered in a spiral arm of the galaxy UGC 01626 - type SAB(rs)c - by F. Ciabattari and E. Mazzoni (Ciabattari et al. 2011CBET.2827....2T) on 2011 September 21.04 (UT) with a 0.5-m Newtonian telescope, in the course of the Italian Supernovae Search Project. The prompt photometric follow-up of SN 2011fu started shortly after the discovery and continued using three ground-based telescopes in India. The majority of the observations were made using the 2-m Himalayan Chandra Telescope (HCT) of the Indian Astronomical Observatory (IAO), Hanle, and the 1-m Sampurnanand Telescope (ST) at the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India. All observations were performed in Bessell UBVRI bands. (1 data file).

  19. A novel method for the synthesis of BiOCl/Bi2Sn2O7 heterojunction photocatalysts with enhanced visible light photocatalytic properties.

    PubMed

    Lv, Dongdong; Zhang, Dafeng; Sun, Qinzhao; Wu, Jiandong; Zhang, Li; Pu, Xipeng; Ma, Huiyan; Dou, Jianmin

    2016-09-23

    A novel simple method was proposed to synthesize BiOCl/Bi2Sn2O7 heterojunction photocatalysts through the treatment of Bi2Sn2O7 with HCl solution of different concentrations. The as-synthesized photocatalysts were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence, x-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflectance spectroscopy. The experimental results show that sheet-like BiOCl particles were obtained after the HCl treatment. Bi2Sn2O7 nanoparticles were distributed on the BiOCl sheets, resulting in the low aggregation of the Bi2Sn2O7 nanoparticles. As compared to BiOCl and Bi2Sn2O7, BiOCl/Bi2Sn2O7 showed enhanced photocatalytic activity under visible light irradiation, which can be attributed to the effective separation of photogenerated electrons and holes due to the formation of a BiOCl/Bi2Sn2O7 heterojunction. In addition, the dominant active species and the photocatalytic mechanism were discussed in detail. PMID:27518499

  20. A novel method for the synthesis of BiOCl/Bi2Sn2O7 heterojunction photocatalysts with enhanced visible light photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Lv, Dongdong; Zhang, Dafeng; Sun, Qinzhao; Wu, Jiandong; Zhang, Li; Pu, Xipeng; Ma, Huiyan; Dou, Jianmin

    2016-09-01

    A novel simple method was proposed to synthesize BiOCl/Bi2Sn2O7 heterojunction photocatalysts through the treatment of Bi2Sn2O7 with HCl solution of different concentrations. The as-synthesized photocatalysts were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, photoluminescence, x-ray photoelectron spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy. The experimental results show that sheet-like BiOCl particles were obtained after the HCl treatment. Bi2Sn2O7 nanoparticles were distributed on the BiOCl sheets, resulting in the low aggregation of the Bi2Sn2O7 nanoparticles. As compared to BiOCl and Bi2Sn2O7, BiOCl/Bi2Sn2O7 showed enhanced photocatalytic activity under visible light irradiation, which can be attributed to the effective separation of photogenerated electrons and holes due to the formation of a BiOCl/Bi2Sn2O7 heterojunction. In addition, the dominant active species and the photocatalytic mechanism were discussed in detail.

  1. Synthesis, characterization and photocatalytic applications of N-, S-, and C-doped SnO2 nanoparticles under ultraviolet (UV) light illumination

    NASA Astrophysics Data System (ADS)

    Nouri, Azita; Fakhri, Ali

    2015-03-01

    N-, S-, and C-doped SnO2 nanoparticles were synthesized via a precipitation method and were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), Transmission Electron Microscope (TEM), UV-vis diffuse reflectance spectral (UV-vis DRS) and Brunauer-Emmett-Teller (BET) techniques. The photocatalytic activities of these SnO2 samples were investigated with methyl orange as the organic pollutant under UV light illumination. UV-vis spectroscopy demonstrated that dopants N,S,C-species can shift the absorption edge to the near UV and visible light region. N,S,C-SnO2 nanoparticles achieved the best photocatalytic efficiency and the most optimal doping ratio was 3 (T/S). The degradation of methyl orange by N,S,C-SnO2 nanoparticles fitted well with the Langmuir-Hinshelwood kinetics model. The results of subsequent experiments indicate that enhanced adsorption ability of light and high separation rate of photo induced charge carriers all play an major role in promotion of photocatalytic activity of N,S,C-SnO2 nanoparticles.

  2. Synthesis, characterization and photocatalytic applications of N-, S-, and C-doped SnO2 nanoparticles under ultraviolet (UV) light illumination.

    PubMed

    Nouri, Azita; Fakhri, Ali

    2015-03-01

    N-, S-, and C-doped SnO2 nanoparticles were synthesized via a precipitation method and were characterized by X-ray diffractometer (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), Transmission Electron Microscope (TEM), UV-vis diffuse reflectance spectral (UV-vis DRS) and Brunauer-Emmett-Teller (BET) techniques. The photocatalytic activities of these SnO2 samples were investigated with methyl orange as the organic pollutant under UV light illumination. UV-vis spectroscopy demonstrated that dopants N,S,C-species can shift the absorption edge to the near UV and visible light region. N,S,C-SnO2 nanoparticles achieved the best photocatalytic efficiency and the most optimal doping ratio was 3 (T/S). The degradation of methyl orange by N,S,C-SnO2 nanoparticles fitted well with the Langmuir-Hinshelwood kinetics model. The results of subsequent experiments indicate that enhanced adsorption ability of light and high separation rate of photo induced charge carriers all play an major role in promotion of photocatalytic activity of N,S,C-SnO2 nanoparticles. PMID:25531405

  3. Highly efficient photocatalysis of p-type Cu{sub 2}ZnSnS{sub 4} under visible-light illumination

    SciTech Connect

    Hou, Xian; Li, Yan Yan, Jian-Jun; Wang, Cheng-Wei

    2014-12-15

    Highlights: • Kesterite CZTS nanocrystal powder was synthesized by one-pot method. • First successful use CZTS nanocrystal powder as photocatalyst. • CZTS shows an efficient photocatalysis under visible light irradiation. • CZTS photocatalyst having excellent stability. - Abstract: Cu{sub 2}ZnSnS{sub 4}, as a very promising p-type semiconductor material, has been extensively used in the study of solar cells owing to its suitable band gap (1.1–1.5 eV), large absorption coefficient of 10{sup 4} cm{sup −1} in the visible spectrum, good photo stability, nontoxicity and relative abundance of the component elements. In this paper, we have successfully synthesized p-type kesterite Cu{sub 2}ZnSnS{sub 4} nanocrystal powder by facile one-pot method, and made our first successful attempt to use Cu{sub 2}ZnSnS{sub 4} nanocrystal powder as a photocatalyst to degradation methyl orange under visible-light irradiation. The exciting results show that in the visible light region, Cu{sub 2}ZnSnS{sub 4} nanocrystal powder possesses an excellent photocatalytic performance of K = 0.0317 min{sup −1}, nearly about 6 times of well known commercial P25 titania powder performance under the same conditions, which suggests that the p-type kesterite Cu{sub 2}ZnSnS{sub 4} nanocrystal would be a promising candidate of photocatalyst.

  4. Production of Light p-Process Isotopes in Neutrino-Irradiated Alpha-Rich Freezeouts

    NASA Astrophysics Data System (ADS)

    Swift, T. P.; Meyer, B. S.; The, L.-S.

    2000-12-01

    The origin of the light, neutron-capture bypassed (p-process) isotopes 92Mo, 94Mo, 96Ru, and 98Ru has long been a mystery. Sites that produce the majority of the p-process isotopes in correct solar proportions have long been known to underproduce the light species [1], thereby suggesting a different origin. The alpha-rich freezeout occurring near a nascent neutron star in Type II supernovae has been proposed [2,3,4]; however, only 92Mo is strongly produced, and it is never the most overproduced isotope, as is required for its site of origin. We explore models of alpha-rich freezeouts that include simultaneous irradiation of the nuclei by the copious neutrinos emitted during the explosion. We find that neutrino-nucleus interactions significantly enhance production of the light p-process species both by affecting the electron-nucleon ratio during the nucleosynthesis and by increasing the charge of nuclei once nuclear quasi-equilibrium clusters have broken. In many models studied, the light p-process isotopes are the most overproduced species, which supports the idea of this being a possible production site. The neutrino fluences required for light p-process isotope production are high--probably somewhat higher than current supernova models allow. Nevertheless, the results are encouraging and suggest further work is needed on this promising site. This work was supported by the NSF Research Experiences for Undergraduates (REU) Site Program through grant AST 96169939 to Florida Tech and the Southeastern Association for Research in Astronomy (SARA). It was also supported by NSF grant AST 9819877 and NASA grant NAG5-4703 at Clemson University. References: [1] Woosley, S. E., and Howard, W. M. 1978, ApJS, 36, 285 [2] Woosley, S. E., and Hoffman, R. D. 1992, ApJ, 395, 202 [3] Fuller, G. M., and Meyer, B. S. 1995, ApJ, 453, 792 [4] Hoffman, R. D., Woosley, S. E., Fuller, G. M., and Meyer, B. S. 1996, ApJ, 460, 478

  5. Acceleration of small, light projectiles (including hydrogen isotopes) to high speeds using a two-stage light gas gun

    SciTech Connect

    Combs, S.K.; Foust, C.R.; Gouge, M.J.; Milora, S.L. )

    1989-01-01

    Small, light projectiles have been accelerated to high speeds using a two-stage light gas gun at Oak Ridge National Laboratory. With 35-mg plastic projectiles (4 mm in diameter), speeds of up to 4.5 km/s have been recorded. The pipe gun'' technique for freezing hydrogen isotopes in situ in the gun barrel has been used to accelerate deuterium pellets (nominal diameter of 4 mm) to velocities of up to 2.85 km/s. The primary application of this technology is for plasma fueling of fusion devices via pellet injection of hydrogen isotopes. Conventional pellet injectors are limited to pellet speeds in the range 1-2 km/s. Higher velocities are desirable for plasma fueling applications, and the two-stage pneumatic technique offers performance in a higher velocity regime. However, experimental results indicate that the use of sabots to encase the cryogenic pellets and protect them for the high peak pressures will be required to reliably attain intact pellets at speeds of {approx}3 km/s or greater. In some limited tests, lithium hydride pellets were accelerated to speeds of up to 4.2 km/s. Also, repetitive operation of the two-stage gun (four plastic pellets fired at {approx}0.5 Hz) was demonstrated for the first time in preliminary tests. The equipment and operation are described, and experimental results and some comparisons with a theoretical model are presented. 17 refs., 6 figs., 2 tabs.

  6. Zirconium—Hafnium Isotope Evidence from Meteorites for the Decoupled Synthesis of Light and Heavy Neutron-rich Nuclei

    NASA Astrophysics Data System (ADS)

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-01

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope 96Zr (<=1ɛ in 96Zr/90Zr) for bulk chondrites and CAIs (~2ɛ). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the 96Zr isotope variations are of nucleosynthetic origin. The 96Zr enrichments are coupled with 50Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A <= 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. 96Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M ⊙) SNII.

  7. ZIRCONIUM—HAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI

    SciTech Connect

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-10

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (≤1ε in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (∼2ε). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ≤ 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ☉}) SNII.

  8. Isotopically Light Organic Carbon in Phanerozoic Black Shales: Diagenetic, Source, or Environmental Signal?

    NASA Astrophysics Data System (ADS)

    Meyers, P. A.

    2011-12-01

    A curious depletion of 13C in the organic matter of marine black shales has been widely recognized ever since the advent of carbon isotope measurements half a century ago. Paleozoic and Mesozoic black shales commonly have del13C values between -29 and -26 permil, whereas modern marine organic matter has values between -22 and -18 permil. The black shale values mimic those of continental organic matter, yet sedimentary settings and Rock-Eval results indicate that the organic matter is marine in origin. This presentation will overview and discuss hypotheses to explain the isotopically light values of the black shales. First, the preferential removal of isotopically heavier organic matter components such as carbohydrates by diagenesis will be examined and shown to be wanting. Second, the possible oxidation of isotopically light methane released from clathrates that would have altered the DIC pool available to phytoplankton will be considered and also be found unlikely. A third possibility - that greater concentrations of CO2 in the greenhouse atmospheres that corresponded with deposition of many black shales allowed greater discrimination against 13C during photosynthesis - will be evaluated from del13C values of bulk carbon and of algal and land-plant biomarker molecules. Finally, the possibility that stronger stratification of the surface ocean may have magnified photic zone recycling of organic matter and reincorporation of its isotopically light carbon into fresh biomass will be considered. Although the fourth possibility is contrary to the conditions of vertical mixing of nutrients that exist in modern upwelling systems and that are responsible for their high productivity, it is consistent with the strongly stratified conditions that accompanied the high productivity that produced the Pliocene-Pleistocene sapropels of the Mediterranean Sea. Because the sapropels and most Phanerozic black shales share del15N values near 0 permil, nitrogen fixation evidently was

  9. Optimization of the size ratio of Sn sphere and laser focal spot for an extreme ultraviolet light source

    SciTech Connect

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

    2008-12-01

    The effect of the ratio of Sn sphere diameter to laser focal spot size (SD/FSS) on conversion efficiency (CE) from laser to in-band (2%) 13.5 nm extreme ultraviolet (EUV) light was investigated by fixing the laser spot size and irradiating variable diameter spheres. It was found that a minimum SD/FSS, i.e., 2.5, is necessary to produce high in-band CE, which is 15% higher than planar targets. Two-dimensional plasma density profile maps showed that the density of the dominant in-band EUV emission region and the size of the surrounding absorbing plasma can be manipulated by geometric effects of the SD/FSS ratio.

  10. A new era for homolytic aromatic substitution: replacing Bu3SnH with efficient light-induced chain reactions.

    PubMed

    Gurry, Michael; Aldabbagh, Fawaz

    2016-04-28

    Herein is a pertinent review of recent photochemical homolytic aromatic substitution (HAS) literature. Issues with using the reductant Bu3SnH in an oxidative process where the net loss of a hydrogen atom occurs is discussed. Nowadays more efficient light-induced chain reactions are used resulting in HAS becoming a synthetic mechanism of choice rivaling organometallic, transition-metal and electrophilic aromatic substitution protocols. The review includes aromatic substitution as part of a tandem or cascade reaction, Pschorr reaction, as well as HAS facilitated by ipso-substitution, and Smiles rearrangement. Recently visible-light photoredox catalysis, which is carried out at room temperature has become one of the most important means of aromatic substitution. The main photoredox catalysts used are polypyridine complexes of Ru(ii) and Ir(iii), although eosin Y is an alternative allowing metal-free HAS. Other radical initiator-free aromatic substitutions have used 9-mesityl-10-methylacridinium ion and N,N-bis(2,6-diisopropylphenyl)perylene-3,4,9,10-bis(dicarboximide) as the photoredox catalyst, UV-light, photoinduced electron-transfer, zwitterionic semiquinone radical anions, and Barton ester intermediates. PMID:27056571

  11. One-step synthesis, characterization, and visible light photocatalytic activity of pure and Zn-doped SnO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Madhan, D.; Rajkumar, P.; Rajeshwaran, P.; Sivarajan, A.; Sangeetha, M.

    2015-08-01

    A one-step microwave irradiation route was used to synthesize undoped and Zn-doped SnO2 nanoparticles for the first time. The morphologies, structures and optical properties of the as-prepared samples were characterized by X-ray powder diffraction, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, UV-Vis spectra and photoluminescence spectra analysis. The results clearly revealed that both the pure and doped samples had a tetragonal rutile-type structure and a space group of P42/mnm have formed directly during the microwave irradiation process. FESEM studies illustrate that both the pristine and Zn-doped SnO2 form in spherical-shaped morphology with an average diameter around 41-32 nm, which is in good agreement with the average crystallite sizes calculated by Scherrer's formula. Optical studies reveal that both pristine and Zn-doped SnO2 direct transitions occur with the bandgap energies in the range of 3.43-3.26 eV. The photocatalytic activities of the pure and Zn-doped SnO2 samples were evaluated by the degradation of methylene blue rhodamine B in an aqueous solution under visible light irradiation. The photocatalytic activity and reusability of Zn (10 wt%)-doped SnO2 was much higher than that of the pure SnO2. The improvement mechanism by zinc doping was also discussed.

  12. Light Isotopes and Trace Organics Analysis of Mars Samples with Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Mahaffy, P.; Niemann, Hasso (Technical Monitor)

    2001-01-01

    Precision measurement of light isotopes in Mars surface minerals and comparison of this isotopic composition with atmospheric gas and other, well-mixed reservoirs such as surface dust are necessary to understand the history of atmospheric evolution from a possibly warmer and wetter Martian surface to the present state. Atmospheric sources and sinks that set these ratios are volcanism, solar wind sputtering, photochemical processes, and weathering. Measurement of a range of trace organic species with a particular focus on species such as amino acids that are the building blocks of terrestrial life are likewise important to address the questions of prebiotic and present or past biological activity on Mars. The workshop topics "isotopic mineralogy" and "biology and pre-biotic chemistry" will be addressed from the point of view of the capabilities and limitations of insitu mass spectrometry (MS) techniques such as thermally evolved gas analysis (TEGA) and gas chromatography (GC) surface experiments using MS, in both cases, as a final chemical and isotopic composition detector. Insitu experiments using straightforward adaptations of existing space proven hardware can provide a substantial improvement in the precision and accuracy of our present knowledge of isotopic composition both in molecular and atomic species in the atmosphere and those chemically bound in rocks and soils. Likewise, detection of trace organic species with greatly improved sensitivity from the Viking GCMS experiment is possible using gas enrichment techniques. The limits to precision and accuracy of presently feasible insitu techniques compared to laboratory analysis of returned samples will be explored. The insitu techniques are sufficiently powerful that they can provide a high fidelity method of screening samples obtained from a diverse set of surface locations such as the subsurface or the interior of rocks for selection of those that are the most interesting for return to Earth.

  13. METHOD OF AND APPARATUS FOR WITHDRAWING LIGHT ISOTOPIC PRODUCT FROM A LIQUID THERMAL DIFFUSION PLANT

    DOEpatents

    Dole, M.

    1959-09-22

    An improved process and apparatus are described for removing enriched product from the columns of a thermal diffusion plant for separation of isotopes. In the removal cycle, light product at the top cf the diffusion columns is circulated through the column tops and a shipping cylinder connected thereto unttl the concertation of enriched product in the cylinder reaches the desired point. During the removal, circulation through the bottoms is blocked bv freezing. in the diffusion cycle, the bottom portion is unfrozen, fresh feed is distributed to the bottoms of the columns, ard heavy product is withdrawn from the bottoms, while the tops of the columns are blocked by freezing.

  14. Gamma rays, X-rays, and optical light from the cobalt and the neutron star in SN 1987A

    NASA Technical Reports Server (NTRS)

    Kumagai, Shiomi; Shigeyama, Toshikazu; Nomoto, Ken'ichi; Itoh, Masayuki; Nishimura, Jun

    1989-01-01

    Recent developments in modeling the X-ray and gamma-ray emission from SN 1987A are discussed by taking into account both the decaying cobalt and the buried neutron star. The light curve and the spectra evolution of X-rays and gamma-rays are well modeled up to day of about 300 if mixing of Co-56 into hydrogen-rich envelope is assumed. However, the 16-28 keV flux observed by Ginga declines very slowly, whereas the spherical mixing model predicts that the flux should have decreased by a large factor at t greater than 300d. It is shown that this problem can be solved if the photoelectric absorption of X-rays is effectively reduced as a result of the formation of chemically inhomogeneous clumps. Based on the adopted hydrodynamical model and the abundance distribution, predictions are offered for future optical, X-ray, and gamma-ray light curves by taking into account other radioactive sources and various types of the central source, e.g., a buried neutron star accreting the reinfalling material or an isolated pulsar.

  15. Synthesis, photocatalytic and antimicrobial properties of SnO2, SnS2 and SnO2/SnS2 nanostructure.

    PubMed

    Fakhri, Ali; Behrouz, Sajjad; Pourmand, Melika

    2015-08-01

    Nanoscale SnO2, SnS2 and SnO2/SnS2 were synthesized by hydrothermal treatment method and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH) and UV-vis spectra. The photocatalytic activity of SnO2, SnS2 and SnO2/SnS2 were tested with Enrofloxacin antibiotic. The tetragonal and hexagonal SnO2 and SnS2 phase was confirmed through XRD, respectively. The photocatalytic results indicated that the SnO2/SnS2 enhanced the photocatalytic activity and could be effectively used as photocatalyst for degradation of Enrofloxacin antibiotic pollutant. The results of antibacterial experiment under visible light irradiation demonstrate that the SnO2/SnS2 nanocomposite exhibit enhanced antibacterial efficiency compared with pure SnO2 and SnS2. The antifungal activity of the nanoscale SnO2, SnS2 and SnO2/SnS2 against Candida albicans was assessed using the disc-diffusion susceptibility tests. It was seen that the antifungal activity of SnO2/SnS2 nanocomposite is higher than the pure SnO2 and SnS2 toward pathogenic C. albicans. PMID:26046748

  16. Non-radiative recombination in Ge{sub 1−y}Sn{sub y} light emitting diodes: The role of strain relaxation in tuned heterostructure designs

    SciTech Connect

    Gallagher, J. D.; Xu, C.; Smith, D. J.; Menéndez, J.; Senaratne, C. L.; Sims, P.; Kouvetakis, J.; Aoki, T.

    2015-06-28

    This paper describes the properties of Ge{sub 1−y}Sn{sub y} light emitting diodes with a broad range of Sn concentrations (y = 0.0–0.11). The devices are grown upon Si(100) platforms using ultra-low temperature deposition of highly reactive Ge and Sn hydrides. The device fabrication adopts two new photodiode designs which lead to optimized performance and enables a systematic study of the effects of strain relaxation on emission efficiency. In contrast with n-Ge/i-Ge{sub 1−y}Sn{sub y}/p-Ge analogs, which in most cases contain two defected interfaces, our designs include a p-layer with composition Ge{sub 1−z}Sn{sub z} chosen to be z < y to facilitate light extraction, but with z close enough to y to guarantee no strain relaxation at the i/p interface. In addition, a Ge{sub 1−x}Sn{sub x} alloy is also used for the n layer, with compositions in the 0 ≤ x ≤ y range, so that defected and non-defected n/i interfaces can be studied. The electroluminescence spectra vs the Sn content y in the intrinsic layer of the diodes exhibit a monotonic shift in the emission wavelength from 1550 nm to 2500 nm. On the other hand, the emission intensities show a complex dependence that cannot be explained solely on the basis of Sn concentrations. Detailed theoretical modeling of these intensities makes it possible to extract recombination lifetimes that are found to be more than three times longer in samples in which strain relaxation has not occurred at the n-i interface, demonstrating the existence of a large non-radiative contribution from the relaxation defects. This finding is particularly significant for direct gap diodes with y > 0.09, for which it is practically impossible to avoid strain relaxation in n-Ge/i-Ge{sub 1−y}Sn{sub y}/p-Ge analogs. The new designs introduced here open the door to the fabrication of highly efficient electrically pumped systems for applications in future generations of integrated photonics.

  17. Facile synthesis of ultrathin SnNb2O6 nanosheets towards improved visible-light photocatalytic H2-production activity.

    PubMed

    Zhou, Chao; Zhao, Yufei; Shang, Lu; Shi, Run; Wu, Li-Zhu; Tung, Chen-Ho; Zhang, Tierui

    2016-07-01

    Ultrathin SnNb2O6 nanosheets with a thickness of ∼3 nm were synthesized via a facile hydrothermal route using ultrathin K4Nb6O17 nanosheets as the precursor. This ultrathin nanosheets with a large specific surface area of 71.1 m(2) g(-1) showed improved visible-light photocatalytic H2-production activity in lactic acid aqueous solution, which is about 4 and 14 times higher than that of 50 nm-thick SnNb2O6 nanosheets and bulk SnNb2O6 powders, respectively. The higher activity of ultrathin nanosheets was mainly attributed to their larger specific surface area and much better charge transfer efficiency. PMID:27284596

  18. In situ synthesis of TiO2/SnO(x)-Au ternary heterostructures effectively promoting visible-light photocatalysis.

    PubMed

    Dong, Zhao; Wu, Minghua; Wu, Jiaying; Ma, Yuanyuan; Ma, Zhenzhen

    2015-07-14

    TiO2/SnOx-Au ternary heterostructures were successfully fabricated via a simple in situ reduction of AuCl4(-) on TiO2 surfaces pre-modified with Sn(2+). The samples were characterized by XRD, TEM, XPS, N2 physical absorption and UV-vis diffuse reflectance spectra. Photocatalytic activity toward degradation of methylene blue (MB) aqueous solution under visible light irradiation was investigated. The results suggested that the highly dispersive and ultrafine Au nanoparticles (NPs) covered with SnOx were deposited onto the surface of TiO2. The heterostructures significantly enhanced the photocatalytic activity compared with the traditional TiO2/Au sample prepared by the impregnation method and also enhanced the activity more than the binary TiO2/SnOx sample. Moreover, the size of the Au NPs could be well controlled by simply tuning the dosage of HAuCl4, and the optimized catalytic activity of the ternary heterostructures was obtained when the dosage of Au was 1% and the Au particle size was ∼2.65 nm. The enhancement of photocatalytic performance could be attributed to the surface plasmon resonance effect of the Au NPs and the electron-sink function of the SnOx, which improve the optical absorption properties as well as photoinduced charge carrier separation, synergistically facilitating the photocatalysis. PMID:26061220

  19. Facile fabrication of p-BiOI/n-Zn{sub 2}SnO{sub 4} heterostructures with highly enhanced visible light photocatalytic performances

    SciTech Connect

    Li, Houran; Jin, Zhao; Sun, Honggang; Sun, Liming; Li, Qingbo; Zhao, Xian; Jia, Chun-Jiang; Fan, Weiliu

    2014-07-01

    Highlights: • The BiOI/Zn{sub 2}SnO{sub 4} photocatalysts were prepared by a mild wet chemical method. • The ZB-1/2 (Zn to Bi molar ratio = 1/2) exhibits the best photocatalytic activity. • The enhanced performance results from high separation of photogenerated carriers. - Abstract: New BiOI/Zn{sub 2}SnO{sub 4} p–n heterojunction photocatalysts were prepared by anchoring n-type Zn{sub 2}SnO{sub 4} nanoparticles on p-type BiOI plates. The physicochemical characteristics of the catalysts were studied by X-ray powder diffraction pattern (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Ultraviolet visible (UV–vis) diffuse reflectance spectroscopy (DRS), nitrogen adsorption–desorption, and photoelectrochemistry measurement. The as-prepared catalysts exhibited excellent photocatalytic activity for the decomposition of methyl orange (MO) under visible light irradiation. The enhanced photocatalytic performance of BiOI/Zn{sub 2}SnO{sub 4} was not only attributed to the matched band potentials but also the interconnected heterojunction of BiOI and Zn{sub 2}SnO{sub 4} nanoparticles.

  20. Fabrication of SnO2-Reduced Graphite Oxide Monolayer-Ordered Porous Film Gas Sensor with Tunable Sensitivity through Ultra-Violet Light Irradiation

    PubMed Central

    Xu, Shipu; Sun, Fengqiang; Yang, Shumin; Pan, Zizhao; Long, Jinfeng; Gu, Fenglong

    2015-01-01

    A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties. PMID:25758292

  1. Non-yrast states and shape co-existence in light Pt isotopes

    NASA Astrophysics Data System (ADS)

    Davidson, P. M.; Dracoulis, G. D.; Kibédi, T.; Byrne, A. P.; Anderssen, S. S.; Baxter, A. M.; Fabricius, B.; Lane, G. J.; Stuchbery, A. E.

    1999-09-01

    Low-lying states in the even-even light platinum isotopes 176Pt, 178Pt, 180Pt and 182Pt have been populated using β+ /EC decay from parent gold nuclei, created in (HI, xn) reactions. State energies, spins and parities and γ-ray branching ratios were determined using γ-ray and electron spectroscopy. Whereas non-yrast states were observed in 178Pt, 180Pt and 182Pt, none were seen in 176Pt. The excitation energies of the observed states are analysed in terms of a band-mixing model, yielding the moments of inertia of the unperturbed bands. Branching ratios and ground-state-band quadrupole moments are calculated and compared with experimental values. The results indicate that the two lowest-lying 0 + states in each of the light Pt isotopes are formed from the mixing of two intrinsic states of different deformation, and other low-lying states can be described as admixtures of rotational states built on these intrinsic states, and on γ-vibrational states.

  2. Charge correlations and isotopic distributions of projectile fragmentation events in Xe124+Sn112 at E/A=50 MeV

    NASA Astrophysics Data System (ADS)

    Hudan, S.; McIntosh, A. B.; Black, J.; Mercier, D.; Metelko, C. J.; Yanez, R.; de Souza, R. T.; Chbihi, A.; Famiano, M.; Frégeau, M. O.; Gauthier, J.; Moisan, J.; Roy, R.; Bianchin, S.; Schwarz, C.; Trautmann, W.; Botvina, A. S.

    2009-12-01

    Ternary breakup of an excited projectile-like fragment produced in mid-peripheral collisions of Xe124 projectiles with Sn112 nuclei at E/A=50 MeV is examined. Charge correlations reveal that symmetric breakups occur with significant probability. By selecting on the parallel velocity of the heaviest fragment we minimize the entrance channel dynamics. Calculations with the statistical decay code GEMINI failed to reproduce the experimental charge correlations for any suitable combination of excitation energy and spin considered. A statistical multifragmentation model (SMM) in which breakup of low-density nuclear matter is assumed was able to reproduce the observed charge correlations. The /Z and isotope distributions of fragments were compared to the results of the SMM calculations. Describing the /Z of heavy fragments (Z>6) within SMM suggests that a reduction of the symmetry energy parameter from γ=25 to 14 MeV is necessary. We observe that the yield of neutron-rich isotopes of heavy fragments is particularly sensitive to the symmetry energy.

  3. Analysis of the early spectra and light curve of SN 1987A

    NASA Technical Reports Server (NTRS)

    Hauschildt, Peter H.; Ensman, Lisa M.

    1994-01-01

    Numerical modeling of supernova spectra, light curves, and hydrodynamics requires physical inputs, numerical techniques, approximations, and assumptions which must be thoroughly understood in order to study the details of supernova explosions. Here, we discuss some of these in the context of the early evolution of supernova 1987A. Gray radiation-hydrodynamics is used to calculate the bolometric light curve and the hydrodynamic evolution of the supernova. Synthetic spectra are then obtained for the resulting density and velocity structure. The spectrum calculations are performed using a special-relativistic treatment of the radiative transfer equation in the comoving frame, line blanketing by about 10(exp 5) spectral lines, and departures from local thermodynamic equilibrium (LTE) for H I, He I, Mg II, and Ca II. We find that we are able to simultaneously fit the early light curve and spectra reasonably well, using a progenitor model from Arnett (1991a), without fine-tuning the free parameters. Temperature structures and radiative equilibrium, non-LTE effects, homologous expansion, and mean opacities are discussed.

  4. White-light luminescence properties of Mg and Sn doped ZnO prepared by thermal oxidation

    SciTech Connect

    Zeng, Jun; Fan, Huiqing; Xue, Jun; Wang, Yangli

    2014-02-01

    Graphical abstract: The PL spectrum of MgSnZnO was measured at room temperature through multi-peak Gaussian fitting, it is found that the broad emission is composed of six peaks. - Highlights: • Mg and Sn doped ZnO are synthesized by thermal oxidation of MgSnZn alloys. • The structure is characterized by XRD and micro-Raman scattering technology. • The optical properties are characterized by photoluminescence spectrum. • The resulting Mg and Sn doped ZnO shows white photoluminescence. - Abstract: This work reports that Mg and Sn doped ZnO (MgSnZnO) are synthesized by thermal oxidation of MgSnZn alloys. The structure and optical properties are characterized by X-ray diffraction (XRD), micro-Raman scattering technology and photoluminescence spectrum. Interestingly, the resulting MgSnZnO shows white photoluminescence. Additionally, the photoluminescence spectrum of MgSnZnO shows two broad emission bands ranging from 360 to 420 nm and 420 to 630 nm, respectively. Through multi-peak Gaussian fitting, it is found that the broad emission is composed of six Gaussian peaks. The six Gaussian peaks are centrered at 383 nm, 397 nm, 455 nm, 516 nm, 560 nm and 614 nm.

  5. Synthesis, features and solar-light-driven photocatalytic activity of TiO2 nanotube arrays loaded with SnO2.

    PubMed

    Sim, Lan Ching; Ng, Kai Wern; Ibrahim, Shaliza; Saravanan, Pichiah

    2014-09-01

    In the present study TiO2 nanotube arrays (TNTs) were loaded with a post-transition metal oxide particles namely SnO2 via incipient wet impregnation method by varying its concentration (1.59 wt%, 2.25 wt% and 2.84 wt%). The photocatalytic activity of the prepared photocatalyst was evaluated for the degradation of methylene blue (MB) in presence of natural solar light irradiation. The morphological analyses revealed that the prepared TNTs had average inner diameter of 109 nm, wall thickness of 15 nm and tube length of 7-10 μm, respectively, while the crystalline phase and Raman spectra confirmed the 100% anatase mineral form of TiO2. Further, the presence of SnO2 in TNTs was confirmed by high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The visible light absorption properties of TNTs improved drastically with increasing SnO2 loadings. The coupling effect of SnO2 and TiO2 significantly enhanced degradation efficiency of MB. An 84% degradation of MB was achieved in 6 h of irradiation under clear sky condition. PMID:25924362

  6. Production of medical isotopes from a thorium target irradiated by light charged particles up to 70 MeV.

    PubMed

    Duchemin, C; Guertin, A; Haddad, F; Michel, N; Métivier, V

    2015-02-01

    The irradiation of a thorium target by light charged particles (protons and deuterons) leads to the production of several isotopes of medical interest. Direct nuclear reaction allows the production of Protactinium-230 which decays to Uranium-230 the mother nucleus of Thorium-226, a promising isotope for alpha radionuclide therapy. The fission of Thorium-232 produces fragments of interest like Molybdenum-99, Iodine-131 and Cadmium-115g. We focus our study on the production of these isotopes, performing new cross section measurements and calculating production yields. Our new sets of data are compared with the literature and the last version of the TALYS code. PMID:25574934

  7. Production of medical isotopes from a thorium target irradiated by light charged particles up to 70 MeV

    NASA Astrophysics Data System (ADS)

    Duchemin, C.; Guertin, A.; Haddad, F.; Michel, N.; Métivier, V.

    2015-02-01

    The irradiation of a thorium target by light charged particles (protons and deuterons) leads to the production of several isotopes of medical interest. Direct nuclear reaction allows the production of Protactinium-230 which decays to Uranium-230 the mother nucleus of Thorium-226, a promising isotope for alpha radionuclide therapy. The fission of Thorium-232 produces fragments of interest like Molybdenum-99, Iodine-131 and Cadmium-115g. We focus our study on the production of these isotopes, performing new cross section measurements and calculating production yields. Our new sets of data are compared with the literature and the last version of the TALYS code.

  8. Selected isotope ratio measurements of light metallic elements (Li, Mg, Ca, and Cu) by multiple collector ICP-MS

    PubMed Central

    Platzner, Thomas I.; Segal, Irina

    2007-01-01

    The unique capabilities of multiple collector inductively coupled mass spectrometry (MC-ICP-MS) for high precision isotope ratio measurements in light elements as Li, Mg, Ca, and Cu are reviewed in this paper. These elements have been intensively studied at the Geological Survey of Israel (GSI) and other laboratories over the past few years, and the methods used to obtain high precision isotope analyses are discussed in detail. The scientific study of isotopic fractionation of these elements is significant for achieving a better understanding of geochemical and biochemical processes in nature and the environment. PMID:17962922

  9. Origin of the granites and related Sn and Pb-Zn polymetallic ore deposits in the Pengshan district, Jiangxi Province, South China: constraints from geochronology, geochemistry, mineral chemistry, and Sr-Nd-Hf-Pb-S isotopes

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Jiang, Shao-Yong; Luo, Lan; Zhao, Kui-Dong; Ma, Liang

    2016-05-01

    The Pengshan Sn and Pb-Zn polymetallic deposits are located in the south margin of the Jiujiang-Ruichang (Jiurui) district of the Middle-Lower Yangtze River Metallogenic Belt in South China. Four large deposits include Huangjinwa, Zengjialong, Jianfengpo, and Zhangshiba, the former three are Sn-dominant deposits which occur as stratiform orebodies in the contact zones of the Pengshan granites and within the country rock strata, whereas Zhangshiba consists of stratiform Pb-Zn orebodies within the Precambrian metasedimentary strata. In this study, we present results on zircon U-Pb ages, major and trace elements, and mineral chemistry as well as Sr-Nd-Hf isotope data of the granites, Pb and S isotopes of both the Sn-dominant and Pb-Zn dominant deposits, and U-Pb dating of cassiterite from the Pengshan district. SHRIMP and LA-ICP-MS zircon U-Pb dating shows that the Pengshan granites were emplaced in the Early Cretaceous (129-128 Ma), which is in good agreement with the U-Pb dating (130-128 Ma) of cassiterite from the Jianfengpo Sn deposit. The Pengshan granites consist mainly of weakly peraluminous highly fractionated I-type affinity granitic rocks. Detailed elemental and isotopic data suggest that the granites formed by partial melting of Mesoproterozoic metamorphic basement materials with minor input of mantle-derived melts. The mineral chemistry of biotite demonstrates that the Pengshan granitic magma had a low oxygen fugacity, thereby precluding the tin dominantly partitioning into the rock-forming silicate minerals and favoring accumulation in the exsolved residual liquid during magma crystallization stages. Sulfur isotopes show a relatively heavy sulfur isotopic composition from 5.8 to 17.6 ‰, and no difference for sulfur isotopes between the Sn deposits (5.8-13.4 ‰, Huangjinwa, Zengjialong, Jianfengpo) and the Pb-Zn deposit (mostly 7.1-13.0 ‰, except for one 17.6 ‰, Zhangshiba). The sulfur isotope data of pyrite from the host sedimentary rocks show

  10. SALT spectroscopic classification of LSQ16acz (= PS16bby = SN 2016bew) as a type-Ia supernova approaching maximum light

    NASA Astrophysics Data System (ADS)

    Jha, S. W.; Pan, Y.-C.; Foley, R. J.; Rest, A.; Scolnic, D.; Kotze, M.

    2016-03-01

    We obtained SALT (+RSS) spectroscopy of LSQ16acz (= PS16bby = SN 2016bew; Baltay et al. 2013, PASP, 125, 683) on 2016 Mar 14.9 UT, covering the wavelength range 340-920 nm. Cross-correlation of the spectrum with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows LSQ16acz is a type-Ia supernova a few days before maximum light.

  11. Pressure dependence of the deuterium isotope effect in the photolysis of formaldehyde by ultraviolet light

    NASA Astrophysics Data System (ADS)

    Nilsson, E. J. K.; Andersen, V. F.; Skov, H.; Johnson, M. S.

    2010-04-01

    The pressure dependence of the relative photolysis rate of HCHO vs. HCDO has been investigated for the first time, using a photochemical reactor at the University of Copenhagen. The dissociation of HCHO vs. HCDO using a UVA lamp was measured at total bath gas pressures of 50, 200, 400, 600 and 1030 mbar. The products of formaldehyde photodissociation are either H2 + CO (molecular channel) or HCO + H (radical channel), and a photolysis lamp was chosen to emit light at wavelengths that greatly favor the molecular channel. The isotope effect in the dissociation, kHCHO/kHCDO, was found to depend strongly on pressure, varying from 1.1 + 0.15/-0.1 at 50 mbar to 1.75±0.10 at 1030 mbar. The results can be corrected for radical channel contribution to yield the kinetic isotope effect for the molecular channel; i.e. the KIE in the production of molecular hydrogen. This is done and the results at 1030 mbar are discussed in relation to previous studies at ambient pressure. In the atmosphere the relative importance of the two product channels changes with altitude as a result of changes in pressure and actinic flux. The study demonstrates that the δD of photochemical hydrogen produced from formaldehyde will increase substantially as pressure decreases.

  12. Shell-model states with seniority ν=3 , 5, and 7 in odd- A neutron-rich Sn isotopes

    SciTech Connect

    Iskra, Ł. W.; Broda, R.; Janssens, R. V. F.; Chiara, C. J.; Carpenter, M. P.; Fornal, B.; Hoteling, N.; Kondev, F. G.; Królas, W.; Lauritsen, T.; Pawłat, T.; Seweryniak, D.; Stefanescu, I.; Walters, W. B.; Wrzesiński, J.; Zhu, S.

    2016-01-01

    Excited states with seniority ν=3, 5, and 7 have been investigated in odd neutron-rich Sn119,121,123,125 isotopes produced by fusion-fission of 6.9-MeV/ACa48 beams with Pb208 and U238 targets and by fission of a U238 target bombarded with 6.7-MeV/ANi64 beams. Level schemes have been established up to high spin and excitation energies in excess of 6 MeV, based on multifold gamma-ray coincidence relationships measured with the Gammasphere array. In the analysis, the presence of isomers was exploited to identify gamma rays and propose transition placements using prompt and delayed coincidence techniques. Gamma decays of the known 27/2- isomers were expanded by identifying new deexcitation paths feeding 23/2+ long-lived states and 21/2+ levels. Competing branches in the decay of 23/2- states toward two 19/2- levels were delineated as well. In Sn119, a new 23/2+ isomer was identified, while a similar 23/2+ long-lived state, proposed earlier in Sn121, has now been confirmed. In both cases, isomeric half-lives were determined with good precision. In the range of ν=3 excitations, the observed transitions linking the various states enabled one to propose with confidence spin-parity assignments for all the observed states. Above the 27/2- isomers, an elaborate structure of negative-parity levels was established reaching the (39/2-), ν=7 states, with tentative spin-parity assignments based on the observed deexcitation paths as well as on general yrast population arguments. In all the isotopes under investigation, strongly populated sequences of positive-parity (35/2+), (31/2+), and (27/2+) states were established, feeding the 23/2+ isomers via cascades of three transitions. In the Sn121,123 isotopes, these sequences also enabled the delineation of higher-lying levels, up to (43/2+) states. In Sn123, a short half-life was determined for the (35/2+) state. Shell-model calculations were carried out for all the odd Sn isotopes, from Sn129 down to Sn119, and the results were

  13. A guide for the laboratory information management system (LIMS) for light stable isotopes--Versions 7 and 8

    USGS Publications Warehouse

    Coplen, Tyler B.

    2000-01-01

    The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program, the Laboratory Information Management System (LIMS) for Light Stable Isotopes, is presented herein. Major benefits of this system include (i) a dramatic improvement in quality assurance, (ii) an increase in laboratory efficiency, (iii) a reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) a decrease in errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for laboratories. LIMS for Light Stable Isotopes is available for both Microsoft Office 97 Professional and Microsoft Office 2000 Professional as versions 7 and 8, respectively. Both source code (mdb file) and precompiled executable files (mde) are available. Numerous improvements have been made for continuous flow isotopic analysis in this version (specifically 7.13 for Microsoft Access 97 and 8.13 for Microsoft Access 2000). It is much easier to import isotopic results from Finnigan ISODAT worksheets, even worksheets on which corrections for amount of sample (linearity corrections) have been added. The capability to determine blank corrections using isotope mass balance from analyses of elemental analyzer samples has been added. It is now possible to calculate and apply drift corrections to isotopic

  14. Production of the doubly magic nucleus Sn100 in fusion and quasifission reactions via light particle and cluster emission channels

    NASA Astrophysics Data System (ADS)

    Kalandarov, Sh. A.; Adamian, G. G.; Antonenko, N. V.; Wieleczko, J. P.

    2014-08-01

    The possibilities of production of the doubly magic nucleus Sn100 in complete fusion and quasifission reactions with stable and radioactive ion beams are investigated within a dinuclear system model. The excitation functions for production of the exotic nuclei 100-103Sn and 112,114Ba via xn, pxn, αxn, and 12,14Cxn emission channels are predicted for future experiments.

  15. Light-travel-time diagnostics in early supernova spectra: substantial mass-loss of the IIb progenitor of SN 2013cu through a superwind

    NASA Astrophysics Data System (ADS)

    Gräfener, G.; Vink, J. S.

    2016-01-01

    The progenitors of Type-IIb supernovae (SNe IIb) are believed to have lost their H-rich envelopes almost completely in the direct pre-SN phase. Recently the first `flash spectrum' of an SN IIb (SN 2013cu) has been presented, taken early enough to study its immediate circumstellar medium (CSM). Similar to a previous study by Groh, we analyse the structure and chemical composition of the optically thick CSM using non-local thermodynamic equilibrium(non-LTE) model atmospheres. For the first time, we take light-travel time effects on the spectrum formation into account, which affect the shapes and strengths of the observable emission lines, as well as the inferred SN luminosity. Based on the new CSM parameters, we estimate a lower limit of ˜0.3 M⊙ for the CSM mass, which is a factor 10-100 higher than previous estimates. The spectral fit implies a CSM in the form of a homogeneous and spherically symmetric superwind whose mass-loss rate exceeds common expectations by up to two orders of magnitude. The derived chemical composition is in agreement with a progenitor that has just left, or is just about to leave the Red-Supergiant stage, confirming the standard picture for the origin of SNe IIb. Due to its extreme mass-loss, the SN progenitor will likely appear as extreme RSG, Luminous Blue Variable, or Yellow Hypergiant. The direct detection of a superwind, and the high inferred CSM mass suggest that stellar wind mass-loss may play an important role in the formation of SNe IIb.

  16. Controlling factors of Ca isotope fractionation in scleractinian corals evaluated by temperature, pH and light controlled culture experiments

    NASA Astrophysics Data System (ADS)

    Inoue, Mayuri; Gussone, Nikolaus; Koga, Yasuko; Iwase, Akihiro; Suzuki, Atsushi; Sakai, Kazuhiko; Kawahata, Hodaka

    2015-10-01

    In this study, the 44Ca/40Ca ratios of Porites australiensis grown under three different culture experiments composed of temperature, pH and light controlled culture experiments are measured. The temperature dependent isotope fractionation of 0.02‰/°C deduced from this study is similar to inorganic aragonite, but the degree of isotope fractionation is about +0.4‰ offset in corals. These observations agree with earlier results on different coral species, suggesting Ca isotope fractionation during Ca transmembrane transport in corals. While in cultured corals a significant temperature dependence of δ44Ca is observed, the relationships between calcium isotope fractionation and pH as well as light intensity are negligible. Therefore variation of δ44Ca in Porites corals is mainly controlled by temperature. A combination of δ44Ca and Sr/Ca of corals in temperature controlled experiments cannot be explained by Rayleigh type fractionation directly from a fluid, which is seawater-like in terms of δ44Ca and Sr/Ca. Through coral-specific biomineralization processes, overall mean δ44Ca of scleractinian corals including previous studies are different from biogenic aragonites secreted by sclerosponges and pteropods, but are comparable with those of bivalves as well as calcitic coccolithophores and foraminifers. These findings are important for better understanding biomineralization in corals and in order to constrain the Ca isotopic composition of oceanic Ca sinks in response to climate changes and associated with shifts of calcite and aragonite seas.

  17. Synergy of metal and nonmetal dopants for visible-light photocatalysis: a case-study of Sn and N co-doped TiO2.

    PubMed

    Zhuang, Huaqiang; Zhang, Yingguang; Chu, Zhenwei; Long, Jinlin; An, Xiaohan; Zhang, Hongwen; Lin, Huaxiang; Zhang, Zizhong; Wang, Xuxu

    2016-04-14

    This paper mainly focuses on the synergistic effect of Sn and N dopants to enhance the photocatalytic performance of anatase TiO2 under visible light or simulated solar light irradiation. The Sn and N co-doped TiO2 (SNT-x) photocatalysts were successfully prepared by the facile sol-gel method and the post-nitridation route in the temperature range of 400-550 °C. All the as-prepared samples were characterized in detail by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, transmission electron microscopy, X-ray photoelectron and electron spin resonance spectroscopy and photoelectrochemical measurements. The characterization results reveal that the co-incorporation of Sn and N atoms remarkably modifies the electronic structure of TiO2, which gives rise to a prominent separation of photogenerated charge carriers and more efficient interfacial charge-transfer reactions in a photocatalytic process. The enhanced photocatalytic activity is attributed to the intensified active oxygen species including hydroxyl radicals (˙OH) and superoxide anion radicals (O2˙(-)) for degradation of organic pollutants. And the result of photocatalytic hydrogen production further confirms the existence of the synergistic effect in the SNT-x samples, because they exhibit higher photocatalytic activity than the sum of N/TiO2 and Sn/TiO2. This work provides a paradigm to consolidate the understanding of the synergistic effect of metal and non-metal co-doped TiO2 in domains of photocatalysis and photoelectrochemistry. PMID:26996319

  18. Light and heavy element isotopic compositions of mainstream SiC grains.

    SciTech Connect

    Amari, S.; Clayton, R. N.; Davis, A. M.; Lewis, R. S.; Pellin, M. J.

    1999-02-03

    Although a variety of types of pre-solar SiC grains have been classified by their C, N, and Si isotopic composition, the majority of such grains are so-called mainstream grains and are believed to have come from asymptotic giant branch stars [1]. We have previously reported the Mo isotopic compositions of presolar SiC grains whose C, N, and Si isotopic compositions were not known [2]. Since most presolar SiC grains fall in the mainstream group, we assumed that these grains were mainstream. The excellent match of the Mo isotopic data with expectations for nucleosynthesis in AGB stars was consistent with this identification. In order to better understand the distribution of isotopic compositions in presolar grains, we have begun to measure heavy element isotopic compositions of presolar SiC grains of known C, N and Si isotopic composition.

  19. VizieR Online Data Catalog: u'BVg'r'i'z' light curves of SN 2008ax (Pastorello+, 2008)

    NASA Astrophysics Data System (ADS)

    Pastorello, A.; Kasliwal, M. M.; Crockett, R. M.; Valenti, S.; Arbour, R.; Itagaki, K.; Kaspi, S.; Gal-Yam, A.; Smartt, S. J.; Griffith, R.; Maguire, K.; Ofek, E. O.; Seymour, N.; Stern, D.; Wiethoff, W.

    2010-02-01

    SN 2008ax is one of the best ever monitored core-collapse SNe, starting with a deep pre-explosion image obtained only 6h prior to the SN discovery of Mostardi et al. (2008CBET.1280....1M). The observational campaign of SN 2008ax started soon after the discovery and covered a period of about 70d. Photometry has been obtained at the 2-m Liverpool Telescope in La Palma (Canary Islands, Spain) and the 60-inch Telescope of the Palomar Observatory. In addition, unfiltered data collected by amateur astronomers have been used in our analysis. These data have been scaled to the Johnson-Bessell V-band or the Sloan r'-band photometry, depending on the sensitivity curves of the CCDs used in these observations. (2 data files).

  20. Control of Surface Plasmon Resonance of Au/SnO2 by Modification with Ag and Cu for Photoinduced Reactions under Visible-Light Irradiation over a Wide Range.

    PubMed

    Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, Hiroshi

    2016-03-18

    Gold particles supported on tin(IV) oxide (0.2 wt% Au/SnO2) were modified with copper and silver by the multistep photodeposition method. Absorption around λ=550 nm, attributed to surface plasmon resonance (SPR) of Au, gradually shifted to longer wavelengths on modification with Cu and finally reached λ=620 nm at 0.8 wt% Cu. On the other hand, the absorption shifted to shorter wavelength with increasing amount of Ag and reached λ=450 nm at 0.8 wt% Ag. These Cu- and Ag-modified 0.2 wt% Au/SnO2 materials (Cu-Au/SnO2 and Ag-Au/SnO2) and 1.0 wt% Au/SnO2 were used for mineralization of formic acid to carbon dioxide in aqueous suspension under irradiation with visible light from a xenon lamp and three kinds of light-emitting diodes with different wavelengths. The reaction rates for the mineralization of formic acid over these materials depend on the wavelength of light. Apparent quantum efficiencies of Cu-Au/SnO2, Au/SnO2, and Ag-Au/SnO2 reached 5.5% at 625 nm, 5.8% at 525 nm, and 5.1% at 450 nm, respectively. These photocatalysts can also be used for selective oxidation of alcohols to corresponding carbonyl compounds in aqueous solution under visible-light irradiation. Broad responses to visible light in formic acid mineralization and selective alcohol oxidation were achieved when the three materials were used simultaneously. PMID:26880569

  1. Certification of butyltins and phenyltins in marine sediment certified reference material by species-specific isotope-dilution mass spectrometric analysis using synthesized 118Sn-enriched organotin compounds

    PubMed Central

    Takatsu, Akiko; Watanabe, Takuro; Aoyagi, Yoshie; Yarita, Takashi; Okamoto, Kensaku; Chiba, Koichi

    2006-01-01

    A new marine sediment certified reference material, NMIJ CRM 7306-a, for butyltin and phenyltin analysis has been prepared and certified by the National Metrological Institute of Japan at the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST). Candidate sediment material was collected at a bay near industrial activity in Japan. After air-drying, sieving, and mixing the material was sterilized with γ-ray irradiation. The material was re-mixed and packaged into 250 glass bottles (15 g each) and these were stored in a freezer at −30 °C. Certification was performed by use of three different types of species-specific isotope-dilution mass spectrometry (SSID–MS)—SSID–GC–ICP–MS, SSID–GC–MS, and SSID–LC–ICP–MS, with 118Sn-enriched organotin compounds synthesized from 118Sn-enriched metal used as a spike. The 118Sn-enriched mono-butyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) were synthesized as a mixture whereas the 118Sn-enriched di-phenyltin (DPhT) and triphenyltin (TPhT) were synthesized individually. Four different extraction methods, mechanical shaking, ultrasonic, microwave-assisted, and pressurized liquid extraction, were adopted to avoid possible analytical bias caused by non-quantitative extraction and degradation or inter-conversion of analytes in sample preparations. Tropolone was used as chelating agent in all the extraction methods. Certified values are given for TBT 44±3 μg kg−1 as Sn, DBT 51 ± 2 μg kg−1 as Sn, MBT 67 ± 3 μg kg−1 as Sn, TPhT 6.9 ± 1.2 μg kg−1 as Sn, and DPhT 3.4 ± 1.2 μg kg−1 as Sn. These levels are lower than in other sediment CRMs currently available for analysis of organotin compounds. PMID:16874473

  2. Tissue S/N ratios and stable isotopes (delta(34)S and delta(15)N) of epilithic mosses (Haplocladium microphyllum) for showing air pollution in urban cities in Southern China.

    PubMed

    Xiao, Hua-Yun; Tang, Cong-Guo; Xiao, Hong-Wei; Wang, Yan-Li; Liu, Xue-Yan; Liu, Cong-Qiang

    2010-05-01

    In urban cities in Southern China, the tissue S/N ratios of epilithic mosses (Haplocladium microphyllum), varied widely from 0.11 to 0.19, are strongly related to some atmospheric chemical parameters (e.g. rainwater SO(4)(2-)/NH(4)(+) ratios, each people SO(2) emission). If tissue S/N ratios in the healthy moss species tend to maintain a constant ratio of 0.15 in unpolluted area, our study cities can be divided into two classes: class I (S/N > 0.15, S excess) and class II (S/N < 0.15, N excess), possibly indicative of stronger industrial activity and higher density of population, respectively. Mosses in all these cities obtained S and N from rainwater at a similar ratio. Sulphur and N isotope ratios in mosses are found significantly linearly correlated with local coal delta(34)S and NH(4)(+)-N wet deposition, respectively, indicating that local coal and animal NH(3) are the major atmospheric S and N sources. PMID:19959268

  3. Light element isotopic compositions of cometary matter returned by the STARDUST mission

    SciTech Connect

    McKeegan, K D; Aleon, J; Bradley, J; Brownlee, D; Busemann, H; Butterworth, A; Chaussidon, M; Fallon, S; Floss, C; Gilmour, J; Gounelle, M; Graham, G; Guan, Y; Heck, P R; Hoppe, P; Hutcheon, I D; Huth, J; Ishii, H; Ito, M; Jacobsen, S B; Kearsley, A; Leshin, L A; Liu, M; Lyon, I; Marhas, K; Marty, B; Matrajt, G; Meibom, A; Messenger, S; Mostefaoui, S; Nakamura-Messenger, K; Nittler, L; Palma, R; Pepin, R O; Papanastassiou, D A; Robert, F; Schlutter, D; Snead, C J; Stadermann, F J; Stroud, R; Tsou, P; Westphal, A; Young, E D; Ziegler, K; Zimmermann, L; Zinner, E

    2006-10-10

    Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild2 particle fragments, however extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Non-terrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is {sup 16}O-enriched like refractory inclusions in meteorites, suggesting formation in the hot inner solar nebula and large-scale radial transport prior to comet accretion in the outer solar system.

  4. Scaling properties of light-cluster production

    NASA Astrophysics Data System (ADS)

    Chajecki, Zbigniew; Youngs, Michael; Coupland, Daniel D.; Lynch, William; Tsang, Betty; Chbihi, Abdelouahad; Danielewicz, Pawel; Desouza, Romualdo; Famiano, Michael; Ghosh, Tilak; Giacherio, B.; Henzl, Vlad; Henzlova, Daniela; Hudan, Sylvie; Kilburn, Micha; Lee, Jenny; Lu, Fei; Rogers, Andrew; Russotto, Paulo; Verde, Giuseppe; Sanetullaev, Alisher; Showalter, Rachel; Sobotka, Lee; Wallace, Mark; Winkelbauer, Jack

    2014-09-01

    We show, using the experimental data from Ca+Ca and Sn+Sn collisions, that ratios of light-particle energy spectra display scaling properties that can be accurately described by effective local chemical potentials. This demonstrates the equivalence of t/3He and n/p spectral ratios and provides an essential test of theoretical predictions of isotopically resolved light-particle spectra. In addition, this approach allows direct comparisons of many theoretical n/p spectral ratios to experiments where charged-particle spectra but not neutron spectra are accurately measured. Such experiments may provide much more quantitative constraints on the density and momentum dependence of the symmetry energy.

  5. Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks

    USGS Publications Warehouse

    Tangalos, G.E.; Beard, B.L.; Johnson, C.M.; Alpers, C.N.; Shelobolina, E.S.; Xu, H.; Konishi, H.; Roden, E.E.

    2012-01-01

    The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero δ56Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (δ56Fe ≈ -1.5 to -0.5‰) aqueous Fe(II) coupled to partial reduction of Fe(III)am by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)am are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)am of approximately -2‰. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-δ56Fe minerals during BIF genesis.

  6. Forensic Applications of Light-Element Stable Isotope Ratios of Ricinus communis Seeds and Ricin Preparations

    SciTech Connect

    Kreuzer, Helen W.; West, Jason B.; Ehleringer, James

    2013-01-01

    Seeds of the castor plant Ricinus communis, also known as castor beans, are of forensic interest because they are the source of the poison ricin. We have tested whether stable isotope ratios of castor seeds and ricin prepared by various methods can be used as a forensic signature. We collected over 300 castor seed samples from locations around the world and measured the C, N, O, and H stable isotope ratios of the whole seeds, oil, and three types of ricin preparations. Our results demonstrate that N isotope ratios can be used to correlate ricin prepared by any of these methods to source seeds. Further, stable isotope ratios distinguished >99% of crude and purified ricin protein samples in pair-wise comparison tests. Stable isotope ratios therefore constitute a valuable forensic signature for ricin preparations.

  7. Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach.

    PubMed

    Giuggiola, Arnaud; Ogée, Jérôme; Rigling, Andreas; Gessler, Arthur; Bugmann, Harald; Treydte, Kerstin

    2016-04-01

    Thinning fosters individual tree growth by increasing the availability of water, light and nutrients. At sites where water rather than light is limiting, thinning also enhances soil evaporation and might not be beneficial. Detailed knowledge of the short- to long-term physiological response underlying the growth responses to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback. We applied a dual isotope approach together with mechanistic isotope models to study the physiological processes underlying long-term growth enhancement of heavily thinned Pinus sylvestris in a xeric forest in Switzerland. This approach allowed us to identify and disentangle thinning-induced changes in stomatal conductance and assimilation rate. At our xeric study site, the increase in stomatal conductance far outweighed the increase in assimilation, implying that growth release in heavily thinned trees is primarily driven by enhanced water availability rather than increased light availability. We conclude that in forests with relatively isohydric species (drought avoiders) that are growing close to their physiological limits, thinning is recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival of forest trees under drought. PMID:26639082

  8. Light stable isotope study of the Roosevelt Hot Springs thermal area, Southwestern Utah

    SciTech Connect

    Rohrs D.T.; Bowman, J.R.

    1980-05-01

    The isotopic composition of hydrogen, oxygen, and carbon has been determined for regional cold springs, thermal fluids, and rocks and minerals from the Roosevelt Hot Springs thermal area. The geothermal system has developed within plutonic granitic rocks and amphibolite facies gneiss, relying upon fracture-controlled permeability for the migration of the thermal fluids. Probably originating as meteoric waters in the upper elevations of the Mineral Mountains, the thermal waters sampled in the production wells display an oxygen isotopic shift of at least +1.2. Depletions of delta /sup 18/O in wole rock, K-feldspar, and biotite have a positive correlation with alteration intensity. W/R mass ratios, calculated from the isotopic shifts of rock and water, range up to 3.0 in a producing horizon of one well, although the K-feldspar has experienced only 30% exchange with the thermal waters. While veinlet quartz has equilibrated with the thermal waters, the /sup 18/O values of K-mica clay, an alteration product of plagioclase, mimic the isotopic composition of K-feldspar and whole rock. This suggests that locally small W/R ratios enable plagioclase to influence its alteration products by isotopic exchange.

  9. High Light Absorption and Charge Separation Efficiency at Low Applied Voltage from Sb-Doped SnO2/BiVO4 Core/Shell Nanorod-Array Photoanodes.

    PubMed

    Zhou, Lite; Zhao, Chenqi; Giri, Binod; Allen, Patrick; Xu, Xiaowei; Joshi, Hrushikesh; Fan, Yangyang; Titova, Lyubov V; Rao, Pratap M

    2016-06-01

    BiVO4 has become the top-performing semiconductor among photoanodes for photoelectrochemical water oxidation. However, BiVO4 photoanodes are still limited to a fraction of the theoretically possible photocurrent at low applied voltages because of modest charge transport properties and a trade-off between light absorption and charge separation efficiencies. Here, we investigate photoanodes composed of thin layers of BiVO4 coated onto Sb-doped SnO2 (Sb:SnO2) nanorod-arrays (Sb:SnO2/BiVO4 NRAs) and demonstrate a high value for the product of light absorption and charge separation efficiencies (ηabs × ηsep) of ∼51% at an applied voltage of 0.6 V versus the reversible hydrogen electrode, as determined by integration of the quantum efficiency over the standard AM 1.5G spectrum. To the best of our knowledge, this is one of the highest ηabs × ηsep efficiencies achieved to date at this voltage for nanowire-core/BiVO4-shell photoanodes. Moreover, although WO3 has recently been extensively studied as a core nanowire material for core/shell BiVO4 photoanodes, the Sb:SnO2/BiVO4 NRAs generate larger photocurrents, especially at low applied voltages. In addition, we present control experiments on planar Sb:SnO2/BiVO4 and WO3/BiVO4 heterojunctions, which indicate that Sb:SnO2 is more favorable as a core material. These results indicate that integration of Sb:SnO2 nanorod cores with other successful strategies such as doping and coating with oxygen evolution catalysts can move the performance of BiVO4 and related semiconductors closer to their theoretical potential. PMID:27203779

  10. Water and light improvement after thinning at a xeric site: Which weights the most? A dual isotope approach

    NASA Astrophysics Data System (ADS)

    Giuggiola, Arnaud; Ogée, Jérôme; Gessler, Arthur; Rigling, Andreas; Bugmann, Harald; Treydte, Kerstin

    2015-04-01

    Reductions in stand density foster individual tree growth due to increases of resources such as water, light and nutrients. Detailed knowledge of the short- to long-term physiological response underlying the growth response to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback. We applied a dual isotope approach together with mechanistic isotope models such as MuSICA to study the physiological processes underlying growth enhancement in a long-term thinning experiment in a xeric Pinus sylvestris forest in Switzerland. This approach allowed for identifying and disentangling changes in stomatal conductance and assimilation rate. Our results indicate that an increase in stomatal conductance outweighs an increase in assimilation, meaning that the observed growth releases in heavy thinned trees at our xeric site are primarily driven by enhanced water availability rather than by the increase in light availability. We conclude that in areas with isohydric species (drought avoiders) that tend to grow close to their physiological limits, thinning is highly recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival rate of individual trees and forests.

  11. Isotope dependence of the vibrational lifetimes of light impurities in Si from first principles

    NASA Astrophysics Data System (ADS)

    West, D.; Estreicher, S. K.

    2007-02-01

    The vibrational lifetimes of a range of H-related defects and interstitial O (Oi) in Si, including isotopic substitutions, are calculated from first principles as a function of temperature. The theoretical approach is explained in detail. The vibrational lifetimes of highest-frequency local vibrational modes of HBC+ , D2* , HD* , DH* , HBC+ , DBC+ , HV•VH , DV•VH , DV•VD , IH2 , ID2 , and various O and Si isotopic combinations of Oi are predicted and the decay channels analyzed. We show that the complete vibrational spectrum of the defects must be known in order to predict vibrational lifetimes. We also show that the “frequency-gap law” is not always valid for high-frequency local vibrational modes.

  12. ISOTOPIC COMPOSITION OF LIGHT NUCLEI IN COSMIC RAYS: RESULTS FROM AMS-01

    SciTech Connect

    Aguilar, M.; Alcaraz, J.; Berdugo, J.; Allaby, J.; Alpat, B.; Ambrosi, G.; Azzarello, P.; Battiston, R.; Anderhub, H.; Ao, L.; Arefiev, A.; Arruda, L.; Barao, F.; Barreira, G.; Basile, M.; Bellagamba, L.; Bartoloni, A.; Becker, R.; Becker, U.; Berges, P.

    2011-08-01

    The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the heliosphere. In this paper, we present measurements of the isotopic ratios {sup 2}H/{sup 4}He, {sup 3}He/{sup 4}He, {sup 6}Li/{sup 7}Li, {sup 7}Be/({sup 9}Be+{sup 10}Be), and {sup 10}B/{sup 11}B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June.

  13. Origin assignment of unidentified corpses by use of stable isotope ratios of light (bio-) and heavy (geo-) elements--a case report.

    PubMed

    Rauch, Elisabeth; Rummel, Susanne; Lehn, Christine; Büttner, Andreas

    2007-05-24

    An unknown male body was found near an expressway in Germany. As different criminalistic and forensic methods (e.g. tooth status, fingerprint or DNA-analysis) could not help to identify the person, multielement stable isotope investigations were applied. The combined analysis of stable isotope ratios of light (H, C, N) and heavy elements (Pb, Sr) on the man's body tissues supported to assign him to Romania. The case report demonstrates an application of multielement-isotope analysis in the forensic fields and its potential. PMID:16529892

  14. Determination of Light Water Reactor Fuel Burnup with the Isotope Ratio Method

    SciTech Connect

    Gerlach, David C.; Mitchell, Mark R.; Reid, Bruce D.; Gesh, Christopher J.; Hurley, David E.

    2007-11-01

    For the current project to demonstrate that isotope ratio measurements can be extended to zirconium alloys used in LWR fuel assemblies we report new analyses on irradiated samples obtained from a reactor. Zirconium alloys are used for structural elements of fuel assemblies and for the fuel element cladding. This report covers new measurements done on irradiated and unirradiated zirconium alloys, Unirradiated zircaloy samples serve as reference samples and indicate starting values or natural values for the Ti isotope ratio measured. New measurements of irradiated samples include results for 3 samples provided by AREVA. New results indicate: 1. Titanium isotope ratios were measured again in unirradiated samples to obtain reference or starting values at the same time irradiated samples were analyzed. In particular, 49Ti/48Ti ratios were indistinguishably close to values determined several months earlier and to expected natural values. 2. 49Ti/48Ti ratios were measured in 3 irradiated samples thus far, and demonstrate marked departures from natural or initial ratios, well beyond analytical uncertainty, and the ratios vary with reported fluence values. The irradiated samples appear to have significant surface contamination or radiation damage which required more time for SIMS analyses. 3. Other activated impurity elements still limit the sample size for SIMS analysis of irradiated samples. The sub-samples chosen for SIMS analysis, although smaller than optimal, were still analyzed successfully without violating the conditions of the applicable Radiological Work Permit

  15. Isotopically nonstationary 13C flux analysis of changes in Arabidopsis thaliana leaf metabolism due to high light acclimation.

    PubMed

    Ma, Fangfang; Jazmin, Lara J; Young, Jamey D; Allen, Doug K

    2014-11-25

    Improving plant productivity is an important aim for metabolic engineering. There are few comprehensive methods that quantitatively describe leaf metabolism, although such information would be valuable for increasing photosynthetic capacity, enhancing biomass production, and rerouting carbon flux toward desirable end products. Isotopically nonstationary metabolic flux analysis (INST-MFA) has been previously applied to map carbon fluxes in photoautotrophic bacteria, which involves model-based regression of transient (13)C-labeling patterns of intracellular metabolites. However, experimental and computational difficulties have hindered its application to terrestrial plant systems. We performed in vivo isotopic labeling of Arabidopsis thaliana rosettes with (13)CO2 and estimated fluxes throughout leaf photosynthetic metabolism by INST-MFA. Plants grown at 200 µmol m(-2)s(-1) light were compared with plants acclimated for 9 d at an irradiance of 500 µmol⋅m(-2)⋅s(-1). Approximately 1,400 independent mass isotopomer measurements obtained from analysis of 37 metabolite fragment ions were regressed to estimate 136 total fluxes (54 free fluxes) under each condition. The results provide a comprehensive description of changes in carbon partitioning and overall photosynthetic flux after long-term developmental acclimation of leaves to high light. Despite a doubling in the carboxylation rate, the photorespiratory flux increased from 17 to 28% of net CO2 assimilation with high-light acclimation (Vc/Vo: 3.5:1 vs. 2.3:1, respectively). This study highlights the potential of (13)C INST-MFA to describe emergent flux phenotypes that respond to environmental conditions or plant physiology and cannot be obtained by other complementary approaches. PMID:25368168

  16. Insights from stable light isotopes on enamel defects and weaning in Pliocene herbivores.

    PubMed

    Franz-Odendaal, Tamara A; Lee-Thorp, Julia A; Chinsamy, Anusuya

    2003-12-01

    A high prevalence of enamel hypoplasia in several herbivores from the early Pliocene Langebaanweg locality, South Africa, indicates general systemic stress during the growing years of life. The presence of several linear enamel hypoplasias per tooth crown in many teeth further suggest that these stress events may be episodic. The delta18O values along tooth crowns of mandibular second molars of Sivatherium hendeyi (Artiodactyla, Giraffidae) were used to investigate the cause of the stress events in this tooth type. Results show that weaning in this fossil giraffid occurred at a similar ontogenetic age to that in extant giraffes, and that the observed enamel hypoplasia towards the base of this tooth type manifested post-weaning. Further, high-resolution oxygen isotope analyses across S. hendeyi third molars suggest that the entire development of defective tooth crowns occurred under conditions of increased aridity in which the cool, rainy part of the seasonal cycle was missing. The high prevalence of this defect in many herbivores suggests that climatic conditions were not favourable. This study reiterates the value of stable isotope analyses in determining both the behaviour of fossil animals and the environmental conditions that prevailed during tooth development. PMID:14660876

  17. METHOD FOR REMOVAL OF LIGHT ISOTOPE PRODUCT FROM LIQUID THERMAL DIFFUSION UNITS

    DOEpatents

    Hoffman, J.D.; Ballou, J.K.

    1957-11-19

    A method and apparatus are described for removing the lighter isotope of a gaseous-liquid product from a number of diffusion columns of a liquid thermal diffusion system in two stages by the use of freeze valves. The subject liquid flows from the diffusion columns into a heated sloping capsule where the liquid is vaporized by the action of steam in a heated jacket surrounding the capsule. When the capsule is filled the gas flows into a collector. Flow between the various stages is controlled by freeze valves which are opened and closed by the passage of gas and cool water respectively through coils surrounding portions of the pipes through which the process liquid is passed. The use of the dual stage remover-collector and the freeze valves is an improvement on the thermal diffusion separation process whereby the fraction containing the lighter isotope many be removed from the tops of the diffusion columns without intercolumn flow, or prior stage flow while the contents of the capsule is removed to the final receiver.

  18. Magnetic Moments of States in 110Sn.

    NASA Astrophysics Data System (ADS)

    Kumbartzki, G. J.

    2016-06-01

    The semi-magic Sn isotopes with Z = 50 are the subject of extensive experimental and theoretical studies. The measured B(E2) values to the 21 + states for the neutron-deficient side of the isotope chain suggest enhanced collectivity when fewer particles are available if the proton shell is not broken. Magnetic moments which are sensitive to proton and neutron contributions to the wave functions of the states could provide critical and relevant information. Magnetic moments were previously measured only for the even stable and a few neutron-rich unstable Sn isotopes. A measurement of the g factors of excited states in 110Sn using the transient field technique was performed at the 88-Inch Cyclotron at the LBNL in Berkeley. The 110Sn nuclei were produced via an α-particle transfer to 106Cd.

  19. Fusion probability for neutron-rich radioactive Sn induced reactions

    SciTech Connect

    Liang, J Felix; Gross, Carl J; Kohley, Zachary W; Shapira, Dan; Varner Jr, Robert L; Allmond, James M; Caraley, Anne L; Lagergren, Karin B; Mueller, Paul Edward

    2012-01-01

    Evaporation residue cross sections for $^{124,126,127,128}$Sn+$^{64}$Ni and $^{132}$Sn+$^{58}$Ni have been measured to study the effects of neutron excess in neutron-rich radioactive nuclei on fusion. For the reactions with $^{64}$Ni, the fusion probability does not decrease with increasing neutron excess in Sn, contrary to the result of the stable beam Sn+Zr measurement. A comparison of the reduced evaporation residue cross sections for $^{126}$Sn+$^{64}$Ni and $^{132}$Sn+$^{58}$Ni, which make the same compound nucleus, shows that the fusion probability is indistinguishable for reactions involving the same atomic elements but different isotope combinations.

  20. Consistent Methodologies for Determining, Relating and Disseminating Light Stable Isotopic Measurement Results: The Carbon Dioxide Example

    NASA Astrophysics Data System (ADS)

    Klinedinst, D. B.; Verkouteren, R. M.

    2001-05-01

    In conjunction with the International Atomic Energy Agency (IAEA), the Atmospheric Chemistry Group (ACG) of National Institute of Standards and Technology (NIST) has coordinated an international CO2 isotope ratio mass spectrometry (IRMS) intercomparison exercise. The results of this exercise, specifically designed to overcome inherent deficiencies revealed by previous intercomparisons, achieved a 2 to 3 fold reduction (improvement) in the reproducibility of reported results across laboratories. Concurrently, the ACG developed and deployed an interactive Web-based data processing interface [http://www.nist.gov/widps-co2]. The interface has open architecture and a transparent, downloadable source code. This data processing system leverages the results of the intercomparison exercise and provides a consistent means by which raw CO2 measurement results are related to the internationally accepted Vienna Pee Dee Belemnite (VPDB) scale. Prominent features of the CO2 intercomparison exercise included: mandatory chemical and operational procedures, reporting of discretionary factors, direct determination of the cross contamination effect within the ion source, the reporting of raw measurement results and centralized data processing. The data reduction interface uses IAEA defined standard procedures for stable isotope measurements and data processing. It incorporates currently defined reference values for selected IAEA and NIST CO2 Reference Materials (RMs). On a routine basis, users can also determine and use assigned values for secondary laboratory standards as input. One or two point (i.e., normalized) realization of the VPDB scale is provided as are optional inputs for the oxygen isotope fractionation factor(α ). We attribute the success of the CO2 intercomparison exercise primarily to the centralized data processing using raw measurements rather than customary result-based data. The centralized processing, in essence, eliminates inconsistencies between integrated

  1. From soil to grape and wine: Variation of light and heavy elements isotope ratios.

    PubMed

    Durante, Caterina; Bertacchini, Lucia; Bontempo, Luana; Camin, Federica; Manzini, Daniela; Lambertini, Paolo; Marchetti, Andrea; Paolini, Mauro

    2016-11-01

    In the development of a geographical traceability model, it is necessary to understand if the value of the monitored indicators in a food is correlated to its origin or if it is also influenced by 'external factors' such as those coming from its production. In this study, a deeper investigation of the trend of direct geographical traceability indicators along the winemaking process of two traditional oenological products was carried out. Different processes were monitored, sampling each step of their production (grape juice, intermediate products and wine). The results related to the determinations of δ(18)O, (D/H)I, (D/H)II, δ(13)C, δ(15)N and (87)Sr/(86)Sr have been reported. Furthermore, correspondence with the isotopic values coming from the respective soil and vine-branch samples have been investigated as well, showing the optimal traceability power of the monitored geographical tracers. PMID:27211693

  2. Photocatalytic performance of Sn-doped TiO{sub 2} nanostructured thin films for photocatalytic degradation of malachite green dye under UV and VIS-lights

    SciTech Connect

    Sayilkan, F.; Asiltuerk, M.; Tatar, P.; Kiraz, N.; Sener, S.; Arpac, E.; Sayilkan, H.

    2008-01-08

    Sn-doped and undoped nano-TiO{sub 2} particles have been synthesized by hydrotermal process without acid catalyst at 225 deg. C in 1 h. Nanostructure-TiO{sub 2} based thin films, contain at different solid ratio of TiO{sub 2} in coating, have been prepared on glass surfaces by spin-coating technique. The structure, surface morphology and optical properties of the thin films and the particles have been investigated by element analysis and XRD, BET and UV/VIS/NIR techniques. The photocatalytic performance of the films was tested for degradation of malachite green dye in solution under UV and VIS-lights. The results showed that the hydrothermally synthesized nano-TiO{sub 2} particles are fully anatase crystalline form and are easily dispersed in water, the coated surfaces have nearly super-hydrophilic properties and, the doping of transition metal ion efficiently improved the photocatalytic performance of the TiO{sub 2} thin film. The results also proved that malachite green is decomposed catalytically due to the pseudo first-order reaction kinetics.

  3. Light Stable Isotopes in Aquifers Affected by Mining Activities in a Brazilian Mining Province

    NASA Astrophysics Data System (ADS)

    Moreira, R. M.; de Carvalho, J. B.

    2013-05-01

    Iron ore is presently a main item in the Brazilian commercial agenda. Large reserves have converted this utility into an important source of export earnings and, secondarily, of raw materials for the domestic industry. Parallel to a boom in mining activities in the last years environmental impacts and a stress on natural resources have soared. A region exhibiting pronouncedly intensive mining activities lies in the central part of the State of Minas Gerais, the third economy of the federation. Mines are sited right beside the capital and neighbor towns amounting to nearly five million inhabitants and a pronounced dependence on groundwater resources. Besides, this region is a water divide enclosing the sources of main contributors to the most strategic fluvial basins in the country. Iron ore is by large the main mineral but other metals (including gold and uranium), as well as non-metals such as limestone, quartz and granite, also occur. Given the significance of this commodity in the country's trade balance and the demand of water resources with acceptable quality for human consumption, the scale of ensuing water use conflicts caused by its exploration is wide ranging and has to be coped with well grounded environmental assessment approaches. Tracer hydrology techniques might be a valuable tool in this context. The characteristics of the area being impacted have been surveyed, including climate and pluviometry, stratigraphic litology, geological structure, use of soil, mineral resources and their exploration, surface and ground water hydrology and their sundry uses. Data to be processed have been procured at local public agencies but as regard local hydrological features, particularly isotopic compositions, ad hoc surveys and methodologies were required. One instance concerns pluviometric isotopy due to the alpine character of the surveyed region altitude and temperature effects might take place. Hence different sites were monitored; cumulative pluviometer samples

  4. The Role of Triaxiality in Shape-Coexistence in Light Krypton Isotopes

    NASA Astrophysics Data System (ADS)

    Fischer, S. M.; Lister

    2008-04-01

    Shape co-existence in lead^1 and krypton^2-4 isotopes has become a cutting-edge topic in understanding the structure of heavier nuclei. Prediction of the relative binding energies of different shapes, and understanding the mixing between configurations presents a discriminating challenge to nuclear theory. In ^72,74,76Kr the occurrence of two well bound shapes has been demonstrated through the observation of low-lying J^π = 0^+ isomers and through radioactive beam Coulomb excitation. Roughly speaking, the shapes correspond to oblate-like and prolate-like configurations. However, the exact shapes, and the role of triaxiality has yet to be fully explored. We present new results from ``in-beam'' heavy-ion spectroscopy on ^74Kr which shows that the population of the isomer is mainly through a gamma vibrational band and that considerable mixing is involved between the states built on the isomer and the gamma band. This research was supported by the DOE Office of Nuclear Physics under contract DE-AC02-06CH11357. ^1A. N. Andreyev et al., Nature 405, 430 (2000) ^2E. Clement et al., Phys. Rev. C 75, 054313 (2007) ^3E. Bouchez et al., Phys. Rev. Lett. 90, 082502 (2003) ^4M. Bender et al., Phys. Rev. C 74, 024312 (2006)

  5. Fe-isotope fractionation in magmatic-hydrothermal mineral deposits: A case study from the Renison Sn-W deposit, Tasmania

    NASA Astrophysics Data System (ADS)

    Wawryk, Christine M.; Foden, John D.

    2015-02-01

    We present 50 new iron isotopic analyses of source granite and mineral separates from the Renison tin deposit in western Tasmania. The aim of the study is to characterise the composition of minerals within a tin deposit associated with a reduced, S-type magma. We have analysed bulk samples of granite, and separates of pyrrhotite, pyrite, arsenopyrite, magnetite, chalcopyrite and siderite by multi-collector inductively coupled mass spectrometry. The isotopic compositions of mineral separates are consistent with theoretical predictions of equilibrium fractionation based on Mössbauer spectroscopy and other parametric calculations. Mineral-mineral pairs yield temperatures of formation that are in agreement with prior detailed fluid inclusion studies, but are spatially inconsistent with declining fluid temperatures with distance from the causative intrusion, limiting the use of Fe isotopes as a potential geothermometer, at least in this case. Comparison of our data with published data from other deposits clearly demonstrates that pyrite, magnetite and chalcopyrite from the hottest ore fluids (>300-400 °C) at Renison are isotopically heavier than minerals sampled from a deposit formed at similar temperatures, but associated with a more oxidised and less differentiated intrusion.

  6. Muon capture on light isotopes measured with the Double Chooz detector

    NASA Astrophysics Data System (ADS)

    Abe, Y.; Abrahão, T.; Almazan, H.; Alt, C.; Appel, S.; Barriere, J. C.; Baussan, E.; Bekman, I.; Bergevin, M.; Bezerra, T. J. C.; Bezrukov, L.; Blucher, E.; Brugière, T.; Buck, C.; Busenitz, J.; Cabrera, A.; Camilleri, L.; Carr, R.; Cerrada, M.; Chauveau, E.; Chimenti, P.; Collin, A. P.; Conover, E.; Conrad, J. M.; Crespo-Anadón, J. I.; Crum, K.; Cucoanes, A. S.; Damon, E.; Dawson, J. V.; de Kerret, H.; Dhooghe, J.; Dietrich, D.; Djurcic, Z.; dos Anjos, J. C.; Dracos, M.; Etenko, A.; Fallot, M.; Felde, J.; Fernandes, S. M.; Fischer, V.; Franco, D.; Franke, M.; Furuta, H.; Gil-Botella, I.; Giot, L.; Göger-Neff, M.; Gomez, H.; Gonzalez, L. F. G.; Goodenough, L.; Goodman, M. C.; Haag, N.; Hara, T.; Haser, J.; Hellwig, D.; Hofmann, M.; Horton-Smith, G. A.; Hourlier, A.; Ishitsuka, M.; Jochum, J.; Jollet, C.; Kaether, F.; Kalousis, L. N.; Kamyshkov, Y.; Kaneda, M.; Kaplan, D. M.; Kawasaki, T.; Kemp, E.; Kryn, D.; Kuze, M.; Lachenmaier, T.; Lane, C. E.; Lasserre, T.; Letourneau, A.; Lhuillier, D.; Lima, H. P.; Lindner, M.; López-Castaño, J. M.; LoSecco, J. M.; Lubsandorzhiev, B.; Lucht, S.; Maeda, J.; Mariani, C.; Maricic, J.; Martino, J.; Matsubara, T.; Mention, G.; Meregaglia, A.; Miletic, T.; Milincic, R.; Minotti, A.; Nagasaka, Y.; Navas-Nicolás, D.; Novella, P.; Oberauer, L.; Obolensky, M.; Onillon, A.; Osborn, A.; Palomares, C.; Pepe, I. M.; Perasso, S.; Porta, A.; Pronost, G.; Reichenbacher, J.; Reinhold, B.; Röhling, M.; Roncin, R.; Rybolt, B.; Sakamoto, Y.; Santorelli, R.; Schilithz, A. C.; Schönert, S.; Schoppmann, S.; Shaevitz, M. H.; Sharankova, R.; Shrestha, D.; Sibille, V.; Sinev, V.; Skorokhvatov, M.; Smith, E.; Soiron, M.; Spitz, J.; Stahl, A.; Stancu, I.; Stokes, L. F. F.; Strait, M.; Suekane, F.; Sukhotin, S.; Sumiyoshi, T.; Sun, Y.; Svoboda, R.; Terao, K.; Tonazzo, A.; Trinh Thi, H. H.; Valdiviesso, G.; Vassilopoulos, N.; Veyssiere, C.; Vivier, M.; von Feilitzsch, F.; Wagner, S.; Walsh, N.; Watanabe, H.; Wiebusch, C.; Wurm, M.; Yang, G.; Yermia, F.; Zimmer, V.; Double Chooz Collaboration

    2016-05-01

    Using the Double Chooz detector, designed to measure the neutrino mixing angle θ13, the products of μ- capture on 12C,13C,14N, and 16O have been measured. Over a period of 489.5 days, 2.3 ×106 stopping cosmic μ- have been collected, of which 1.8 ×105 captured on carbon, nitrogen, or oxygen nuclei in the inner detector scintillator or acrylic vessels. The resulting isotopes were tagged using prompt neutron emission (when applicable), the subsequent β decays, and, in some cases, β -delayed neutrons. The most precise measurement of the rate of 12C(μ-,ν ) 12B to date is reported: 6 .57-0.21+0.11×103s-1 , or (17 .35-0.59+0.35)% of nuclear captures. By tagging excited states emitting γ s , the ground state transition rate to 12B has been determined to be 5 .68-0.23+0.14 ×103s-1 . The heretofore unobserved reactions 12C(μ-,ν α ) 8Li,13C(μ-,ν n α ) 8Li , and 13C(μ-,ν n ) 12B are measured. Further, a population of β n decays following stopping muons is identified with 5.5 σ significance. Statistics limit our ability to identify these decays definitively. Assuming negligible production of 8He, the reaction 13C(μ-,ν α ) 9Li is found to be present at the 2.7 σ level. Limits are set on a variety of other processes.

  7. Lighting.

    SciTech Connect

    United States. Bonneville Power Administration.

    1992-09-01

    Since lighting accounts for about one-third of the energy used in commercial buildings, there is opportunity to conserve. There are two ways to reduce lighting energy use: modify lighting systems so that they used less electricity and/or reduce the number of hours the lights are used. This booklet presents a number of ways to do both. Topics covered include: reassessing lighting levels, reducing lighting levels, increasing bulb & fixture efficiency, using controls to regulate lighting, and taking advantage of daylight.

  8. SN 1991T: Reflections of past glory

    NASA Technical Reports Server (NTRS)

    Schmidt, Brian P.; Kirshner, Robert P.; Leibundgut, Bruno; Wells, Lisa A.; Porter, Alain C.; Ruiz-Lapuente, Pilar; Challis, Peter; Filippenko, Alexei V.

    1994-01-01

    We have obtained photometry and spectra of SN 1991T which extend more than 1000 days past maximum light, by far the longest of SN Ia has been followed. Although SN 1991T exhibited nearly photometric behavior in the first 400 days following maximum, by 600 days its decline had slowed, and by 950 days the supernova brightness was consistent with a constant apparent magnitude of m(sub B) = 21.30. Spectra near maximum showed minor variations on the SN Ia theme which grew less conspicuous during the exponential decline. At 270 days the nebular spectrum was composed of Fe and Co lines common to SN Ia. However, by 750 days past maximum light, these lines had shifted in wavelength, and were superposed on a strong blue continuum. The luminosity of SN 1991T at 950 days is more than (9.0 x 10(exp 38)(D/13 Mpc)(2) ergs/s with a rate of decline of less than 0.04 mag per 100 days. We show that this emission is likely to be light that was emitted by SN 1991T near maximum light which has reflected from foreground dust, much like the light echos observed around SN 1987A.

  9. Light effects on the isotopic fractionation of skeletal oxygen and carbon in the cultured zooxanthellate coral, Acropora: implications for coral-growth rates

    NASA Astrophysics Data System (ADS)

    Juillet-Leclerc, A.; Reynaud, S.

    2009-11-01

    Skeletal isotopic and metabolic measurements of the branching coral Acropora cultured in constant conditions and subjected to two light intensities were revisited. We individually compared the data recorded at low light (LL) and high light (HL) for 24 colonies, all derived from the same parent colony. Metabolic and isotopic responses to the different light levels were highly variable. High light led to productivity enhancement, reduction of surface extension, doubling of aragonite deposited weight and increased δ18O levels in all nubbins; responses in respiration and δ13C were not clear. The partitioning of the colonies into two groups, one showing a δ13C increase and the other a δ13C decrease with increased light, revealed common behaviors. Samples showing an increase in δ13C were associated with the co-variation of low surface extension and high productivity while samples showing a decrease in δ13C were associated with the co-variation of higher surface extension and limited productivity. This experiment, which allowed for the separation of temperature and light effects on the coral, highlighted the significant light influences on both skeletal δ18O and δ13C. The high scattering of inter-colony δ18O observed at one site could be due to the differing photosynthetic responses of symbiotic algal assemblages. The δ13C responses could also be related to differing algal distributions in different skeletal portions. Our results were compared to observations by Gladfelter on Acropora cervicornis (1982). Both set of results highlight the relationships between coral-growth rates, micro-structures and photosynthetic activity. It appears that extension growth and accretion are two separate growth modes, and accretion is light-enhanced while extension is light-repressed. There are multiple consequences of these findings for paleoclimatic reconstructions involving corals.

  10. On strontium isotopic anomalies and odd-A p-process abundances. [in solar system

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1978-01-01

    Several aspects of the nucleosynthesis of Sr isotopes are considered in an attempt to shed light on the problem of the Sr isotopic anomalies discovered in an inclusion of the Allende meteorite. Decomposition of the Sr isotopes into average r-, s-, and p-process nucleosynthetic classes is performed. It is suggested that the Allende inclusion most likely has an excess of s-process Sr and that the initial Sr-87/Sr-86 isotopic ratio is probably slightly more primitive than basaltic achondrites. The results also show that Sn-115 is mostly due to the r-process and that odd-A yields are very small. It is concluded that if the Sr anomaly in the inclusion is an average s enhancement, it argues somewhat in favor of a model of gas/dust fractionation of s and r isotopes during accumulation of the inclusion parent in the protosolar cloud.

  11. Spectra of two very old supernovae - SN 1986J and SN 1980K

    NASA Technical Reports Server (NTRS)

    Leibundgut, Bruno; Kirshner, Robert P.; Pinto, Philip A.; Rupen, Michael P.; Smith, R. Chris

    1991-01-01

    Spectra are presented for SN 1986J in NGC 891, observed 4 and 7 years after the explosion, and SN 1980K, observed 9 years after maximum light. A narrow-line and a broad-line component are noted in SN 1986J; these are respectively attributed to a circumstellar shell and the actual stellar interior (without hydrogen). SN 1980K continues to emit in very broad lines. Comparison with earlier observations suggests that this SN halted its exponential flux decline in the early 1980s, and is currently emitting at a constant rate. In both SNs studies, the identity of the energy source which sustains emission remains uncertain.

  12. Magic nucleus 132Sn and its one-neutron-hole neighbor 131Sn.

    PubMed

    Bhattacharyya, P; Daly, P J; Zhang, C T; Grabowski, Z W; Saha, S K; Broda, R; Fornal, B; Ahmad, I; Seweryniak, D; Wiedenhöver, I; Carpenter, M P; Janssens, R V; Khoo, T L; Lauritsen, T; Lister, C J; Reiter, P; Blomqvist, J

    2001-08-01

    Prompt and delayed gamma-ray cascades in doubly magic 132Sn and its neighbor 131Sn have been studied at Gammasphere using a 248Cm fission source. Isotopic assignments of unknown gamma rays were based on coincidences with known transitions in A = 112-116 Pd fission partners. The yrast level spectra of both tin nuclei are interpreted using empirical nucleon-nucleon interactions from the 132Sn and 208Pb regions. Results include identification of the (nuf(7/2)h(-1)(11/2))9(+) aligned state in 132Sn and of extensive (nuf(7/2)h(-2)(11/2)), (nuf(7/2)d(-1)(3/2)h(-1)(11/2)) and (nuh(-1)(11/2)x3(-)) multiplets in 131Sn. The previously reported beta(-) decay of an unusual 131In high-spin isomer to levels in 131Sn is also elucidated. PMID:11497825

  13. Light effects on the isotopic fractionation of skeletal oxygen and carbon in the cultured zooxanthellate coral, Acropora: implications for coral-growth rates

    NASA Astrophysics Data System (ADS)

    Juillet-Leclerc, A.; Reynaud, S.

    2010-03-01

    Skeletal isotopic and metabolic measurements of the branching coral Acropora cultured in constant conditions and subjected to two light intensities were revisited. We individually compared the data recorded at low light (LL) and high light (HL) for 24 colonies, all derived from the same parent colony. Metabolic and isotopic responses to the different light levels were highly variable. High light led to productivity enhancement, reduction of surface extension, doubling of aragonite deposited weight and increased δ18O levels in all nubbins; responses in respiration and δ13C were not clear. The partitioning of the colonies cultured at HL into two groups, one showing a δ13C enrichment and the other a δ13C decrease revealed common behaviors. Samples showing an increase in δ13C were associated with the co-variation of low surface extension and high productivity while samples showing a decrease in δ13C were associated with the co-variation of higher surface extension and limited productivity. This experiment, which allowed for the separation of temperature and light effects on the coral, highlighted the significant light influences on both skeletal δ18O and δ13C. The high scattering of inter-colony δ18O observed at one site could be due to the differing photosynthetic responses of symbiotic algal assemblages. We compared our results with observations by Gladfelter on Acropora cervicornis (1982). Both set of results highlight the relationships between coral-growth rates, micro-structures and photosynthetic activity. It appears that extension growth and skeleton thickening are two separate growth modes, and thickening is light-enhanced while extension is light-suppressed. There are multiple consequences of these findings for paleoclimatic reconstructions involving corals.

  14. Structural change induced by thermal annealing of red-light-emitting ZnSnF6 • 6H2O:Mn4+ hexahydrate phosphor

    NASA Astrophysics Data System (ADS)

    Hoshino, Ryosuke; Nakamura, Toshihiro; Adachi, Sadao

    2016-05-01

    Effects of thermal annealing on the red-emitting ZnSnF6 • 6H2O:Mn4+ hexahydrate phosphor properties were investigated using X-ray diffraction measurement (XRD), photoluminescence (PL) analysis, and Raman scattering spectroscopy. Thermal annealing was performed at T a = 50 to 400 °C in air for 1 h. Mn4+-related red emission wavelengths were redshifted about 5 nm after annealing at T a ≥ 200 °C with greatly decreased emission intensities. This change in PL spectral feature was attributed to the dehydration of the hexahydrate phosphor, supported by the XRD and Raman scattering results. The XRD and PL intensity analyses determined thermal decomposition energies of ∼0.3 eV from the ZnSnF6 • 6H2O hexahydrate to anhydrate and of ∼0.9 eV from the ZnSnF6 anhydrate to metallic fluorid/oxide (ZnF2/SnO2). A comparative discussion was given on the PL properties of two different Mn4+-activated phosphors, Ba–IV–F6:Mn4+ anhydrate and Zn–IV–F6 • 6H2O:Mn4+ hexahydrate phosphors with IV = Si, Ge, and Sn.

  15. Quality assurance and quality control in light stable isotope laboratories: A case study of Rio Grande, Texas, water samples

    USGS Publications Warehouse

    Coplen, T.B.; Qi, H.

    2009-01-01

    New isotope laboratories can achieve the goal of reporting the same isotopic composition within analytical uncertainty for the same material analysed decades apart by (1) writing their own acceptance testing procedures and putting them into their mass spectrometric or laser-based isotope-ratio equipment procurement contract, (2) requiring a manufacturer to demonstrate acceptable performance using all sample ports provided with the instrumentation, (3) for each medium to be analysed, prepare two local reference materials substantially different in isotopic composition to encompass the range in isotopic composition expected in the laboratory and calibrated them with isotopic reference materials available from the International Atomic Energy Agency (IAEA) or the US National Institute of Standards and Technology (NIST), (4) using the optimum storage containers (for water samples, sealing in glass ampoules that are sterilised after sealing is satisfactory), (5) interspersing among sample unknowns local laboratory isotopic reference materials daily (internationally distributed isotopic reference materials can be ordered at three-year intervals, and can be used for elemental analyser analyses and other analyses that consume less than 1 mg of material) - this process applies to H, C, N, O, and S isotope ratios, (6) calculating isotopic compositions of unknowns by normalising isotopic data to that of local reference materials, which have been calibrated to internationally distributed isotopic reference materials, (7) reporting results on scales normalised to internationally distributed isotopic reference materials (where they are available) and providing to sample submitters the isotopic compositions of internationally distributed isotopic reference materials of the same substance had they been analysed with unknowns, (8) providing an audit trail in the laboratory for analytical results - this trail commonly will be in electronic format and might include a laboratory

  16. Quality assurance and quality control in light stable isotope laboratories: a case study of Rio Grande, Texas, water samples.

    PubMed

    Coplen, Tyler B; Qi, Haiping

    2009-06-01

    New isotope laboratories can achieve the goal of reporting the same isotopic composition within analytical uncertainty for the same material analysed decades apart by (1) writing their own acceptance testing procedures and putting them into their mass spectrometric or laser-based isotope-ratio equipment procurement contract, (2) requiring a manufacturer to demonstrate acceptable performance using all sample ports provided with the instrumentation, (3) for each medium to be analysed, prepare two local reference materials substantially different in isotopic composition to encompass the range in isotopic composition expected in the laboratory and calibrated them with isotopic reference materials available from the International Atomic Energy Agency (IAEA) or the US National Institute of Standards and Technology (NIST), (4) using the optimum storage containers (for water samples, sealing in glass ampoules that are sterilised after sealing is satisfactory), (5) interspersing among sample unknowns local laboratory isotopic reference materials daily (internationally distributed isotopic reference materials can be ordered at three-year intervals, and can be used for elemental analyser analyses and other analyses that consume less than 1 mg of material) - this process applies to H, C, N, O, and S isotope ratios, (6) calculating isotopic compositions of unknowns by normalising isotopic data to that of local reference materials, which have been calibrated to internationally distributed isotopic reference materials, (7) reporting results on scales normalised to internationally distributed isotopic reference materials (where they are available) and providing to sample submitters the isotopic compositions of internationally distributed isotopic reference materials of the same substance had they been analysed with unknowns, (8) providing an audit trail in the laboratory for analytical results - this trail commonly will be in electronic format and might include a laboratory

  17. Patterns of Storage, Synthesis and Changing Light Levels Revealed by Carbon Isotope Microsampling within Eocene Metasequoia Tree Rings

    NASA Astrophysics Data System (ADS)

    Jahren, H.; Sternberg, L.

    2005-12-01

    Fossil tree rings from Axel Heiberg Island were microanalyzed for δ13C value in order to assess patterns of tree growth and carbon storage within the Middle Eocene (~45 Ma) Arctic paleoenvironment. Wood from four Metasequoia-type individuals was subsampled for analysis: each individual fossil consisted of between 4 and 10 large (~1 cm thick) consecutive tree rings. One of the fossils displayed an obvious concentric pattern, allowing for the determination of the direction of growth with isotopic pattern. Each ring was divided into ~1 mm thick subsamples, resulting in 5-10 δ13C value determinations per period of ring growth (i.e., growing season). All rings revealed a distinct pattern that was characteristic across growing seasons and across individual fossils. Early in the season, δ13C was at its highest value but descended systematically and sharply to its lowest value at the end of the growing season. Total decrease ranged between 3 and 5 ‰ over the course of each growing season. Identical patterns were observed in the δ13C value of alpha-cellulose isolated from each subsample, indicating that the trends observed did not represent changing levels of secondary metabolites, but rather a seasonal adjustment in the bulk source of carbon used during biosynthesis. Our results are consistent with the following annual pattern of wood synthesis 1.) complete dependence on the mobilization of stored carbon compounds early in the growing season; 2.) systematically increasing use of actively-acquired photosynthate during the growing season; 3.) complete reliance on active photosynthate by the end of the growing season. An additional and significant source of 13C discrimination is declining light levels late in the growing season, and likely contributes to the extreme pattern of δ13C decrease seen across each ring. Our results mimic those seen from modern broadleaf deciduous trees (Helle & Schlesser 2004), but differ from those seen in modern conifers (Barbour et al 2002

  18. Effects of interlayer Sn-Sn lone pair interaction on the band gap of bulk and nanosheet SnO

    NASA Astrophysics Data System (ADS)

    Umezawa, Naoto; Zhou, Wei

    2015-03-01

    Effects of interlayer lone-pair interactions on the electronic structure of SnO are firstly explored by the density-functional theory. Our comprehensive study reveals that the band gap of SnO opens as increase in the interlayer Sn-Sn distance. The effect is rationalized by the character of band edges which consists of bonding and anti-bonding states from interlayer lone pair interactions. The band edges for several nanosheets and strained double-layer SnO are estimated. We conclude that the double-layer SnO is a promising material for visible-light driven photocatalyst for hydrogen evolution. This work is supported by the Japan Science and Technology Agency (JST) Precursory Research for Embryonic Science and Technology (PRESTO) program.

  19. A Luminous Peculiar Type Ia Supernova SN 2011hr: More Like SN 1991T or SN 2007if?

    NASA Astrophysics Data System (ADS)

    Zhang, Ju-Jia; Wang, Xiao-Feng; Sasdelli, Michele; Zhang, Tian-Meng; Liu, Zheng-Wei; Mazzali, Paolo A.; Meng, Xiang-Cun; Maeda, Keiichi; Chen, Jun-Cheng; Huang, Fang; Zhao, Xu-Lin; Zhang, Kai-Cheng; Zhai, Qian; Pian, Elena; Wang, Bo; Chang, Liang; Yi, Wei-Min; Wang, Chuan-Jun; Wang, Xue-Li; Xin, Yu-Xin; Wang, Jian-Guo; Lun, Bao-Li; Zheng, Xiang-Ming; Zhang, Xi-Liang; Fan, Yu-Feng; Bai, Jin-Ming

    2016-02-01

    Photometric and spectroscopic observations of a slowly declining, luminous Type Ia supernova (SN Ia) SN 2011hr in the starburst galaxy NGC 2691 are presented. SN 2011hr is found to peak at {M}B\\=\\-19.84+/- 0.40 {mag}, with a postmaximum decline rate Δm15(B) = 0.92 ± 0.03 mag. From the maximum-light bolometric luminosity, L\\=\\(2.30+/- 0.90)× {10}43 {erg} {{{s}}}-1, we estimate the mass of synthesized 56Ni in SN 2011hr to be M{(}56{Ni})\\=\\1.11+/- 0.43 {M}⊙ . SN 2011hr appears more luminous than SN 1991T at around maximum light, and the absorption features from its intermediate-mass elements (IMEs) are noticeably weaker than those of the latter at similar phases. Spectral modeling suggests that SN 2011hr has IMEs of ˜0.07 {M}⊙ in the outer ejecta, which is much lower than the typical value of normal SNe Ia (i.e., 0.3-0.4 {M}⊙ ) and is also lower than the value of SN 1991T (i.e., ˜0.18 {M}⊙ ). These results indicate that SN 2011hr may arise from a Chandrasekhar-mass white dwarf progenitor that experienced a more efficient burning process in the explosion. Nevertheless, it is still possible that SN 2011hr may serve as a transitional object connecting the SN 1991T-like SNe Ia with a superluminous subclass like SN 2007if given that the latter also shows very weak IMEs at all phases.

  20. Variation of the light stable isotopes in the superior and inferior grains of rice (Oryza sativa L.) with different geographical origins.

    PubMed

    Chen, Tianjin; Zhao, Yan; Zhang, Weixing; Yang, Shuming; Ye, Zhihua; Zhang, Guoyou

    2016-10-15

    Trying to explore a new research angle to increase the resolution and accessibility of isotopic based traceability technique, light stable isotopes (δ(13)C, δ(15)N, δD and δ(18)O) in the superior (SS) and inferior (IS) grains of a rice cultivar Daohuaxiang were analyzed with relatively limited sample numbers and adjacent sites in Fujin and Wuchang, Heilongjiang Province, PR China. Distribution of δ(13)C, δ(15)N and δ(18)O in the SS and IS grains were found to be different. δ(18)O and δD can discriminate rice cultivation areas. However, δ(13)C and δ(15)N values in Fujin and Wuchang overlapped when the differences between SS and IS were considered, thus δ(13)C and δ(15)N cannot be used to discriminate cultivation areas. This exploratory study indicate the variation of the light stable isotopes in the grains located on different panicle positions could be used to discriminate the geographical origin but still need further systematic consideration and verification. PMID:27173539

  1. Tin isotope fractionation in terrestrial cassiterites

    SciTech Connect

    McNaughton, N.J. ); Rosman, K.J.R. )

    1991-02-01

    The isotopic composition of tin has been measured in a range of cassiterites and pure reagents to assess the extent to which this element is isotopically fractionated in natural processes. Only two samples showed evidence of isotopic fractionation, and it is concluded that natural Sn isotope fractionation is small and uncommon. This feature reflects the world dominance of Sn-oxide ores Sn-sulfide ores, and the highly efficient processes of Sn dissolution and precipitation which negate equilibrium and kinetic fractionation of Sn isotopes, respectively. The two samples which show slight fractionation are a highly purified and cassiterite from the Archaean Greenbushes pegmatite, Western Australia. The latter Sn is 0.15{per thousand} per mass unit heavier than the authors laboratory standard, whereas the former is 0.12{per thousand} per mass unit lighter. Although the cassiterite fractionation is considered to result from natural geological processes, the fractionation of purified Sn may be either natural or relate to the purification process, the fractionation of this magnitude has a negligible effect on the current best estimate of the atomic weight of Sn, but it does place a lower limit on its associated accuracy.

  2. Beta Decay of 101Sn

    SciTech Connect

    Kavatsyuk, O.; Mazzocchi, C.; Janas, Z.; Banu, A.; Batist, L.; Becker, F.; Blazhev, A.; Bruchle, W.; Doring, J.; Faestermann, T.; Gorska, M.; Grawe, H.; Jungclaus, A.; Karny, M.; Kavatsyuk, M.; Klepper, O.; Kirchner, R.; La Commara, M.; Miernik, K.; Mukha, I.; Plettner, C.; Plochocki, A.; Roeckl, E.; Romoli, M.; Rykaczewski, Krzysztof Piotr; Schadel, M.; Schmidt, K.; Schwengner, R.; Zylicz, J.

    2007-01-01

    The {beta} decay of the very neutron-deficient isotope 101Sn was studied at the GSI on-line mass separator using silicon detectors for recording charged particles and germanium detectors for {gamma}-ray spectroscopy. Based on the {beta}-delayed proton data the production cross-section of 101Sn in the 50Cr + 58Ni fusion-evaporation reaction was determined to be about 60nb. The half-life of 101Sn was measured to be 1.9(3)s. For the first time {beta}-delayed {gamma}-rays of 101Sn were tentatively identified, yielding weak evidence for a cascade of 352 and 1065keV transitions in 101In. The results for the 101Sn decay as well as those from previous work on the 103Sn decay are discussed by comparing them to predictions obtained from shell model calculations employing a new interaction in the 88Sr to 132Sn model space.

  3. Experimental reconstruction of excitation energies of primary hot isotopes in heavy ion collisions near the Fermi energy

    NASA Astrophysics Data System (ADS)

    Rodrigues, M. R. D.; Lin, W.; Liu, X.; Huang, M.; Zhang, S.; Chen, Z.; Wang, J.; Wada, R.; Kowalski, S.; Keutgen, T.; Hagel, K.; Barbui, M.; Bottosso, C.; Bonasera, A.; Natowitz, J. B.; Materna, T.; Qin, L.; Sahu, P. K.; Schmidt, K. J.

    2013-09-01

    The excitation energies of the primary hot isotopes in multifragmentation events are experimentally reconstructed in the reaction system 64Zn + 112Sn at 40 MeV/nucleon. A kinematical focusing method is employed to evaluate the multiplicities of the evaporated light particles associated with isotopically identified fragments with 3≤Z≤14. Angular distributions of the velocity spectra of light charged particles and neutrons associated with trigger isotopes are examined. A moving source fit is used to separate the kinematically correlated particles, evaporated from the parents of the detected isotopes, from the uncorrelated particles originating from other sources. The latter are evaluated experimentally relative to those in coincidence with the Li isotopes. A parameter, k, is used to adjust the yield of the uncorrelated particles for different trigger isotopes. For each experimentally detected isotope, the multiplicities, apparent temperatures, and k values for n, p, d, t, and α particles are extracted. Using the extracted values, the excitation energies of the primary hot isotopes are reconstructed employing a Monte Carlo method. The extracted excitation energies are in the range of 1 to 4 MeV/nucleon but show a significant decreasing trend as a function of A for a given Z of the isotopes. The results are compared with those of antisymmetrized molecular dynamics (AMD) and statistical multifragmentation model (SMM) simulations. While some of the experimental characteristics are predicted partially by each model, neither simulation reproduces the overall characteristics of the experimental results.

  4. Global properties of nuclei from {sup 100}Sn to {sup 132}Sn

    SciTech Connect

    Isakov, V. I.

    2013-07-15

    The paper presents the results of both microscopical and semi-empirical calculations of single-particle characteristics, nuclear binding, and one-nucleon separation energies of nuclei, as well as their root-mean-square radii, energy levels and transition rates in the long chain of Sn isotopes. We consider nuclei from the extremely neutron-deficient {sup 100}Sn up to neutron excess {sup 136}Sn, where the experimental information is available by now. The comprehensive comparison with the experimental data is carried out.

  5. Precision measurement of isospin diffusion in peripheral Sn+Sn collisions at 70 MeV/u

    NASA Astrophysics Data System (ADS)

    Winkelbauer, Jack Robert

    Much effort has been undertaken recently to improve constraints on the symmetry energy term in the Nuclear Equation of State (EOS). Specifically, the behavior of the symmetry energy above and below nuclear saturation density plays a significant role in the properties of neutron stars, the structure of heavy nuclei, and the dynamics of nuclear reactions. The tendency for neutrons to drift from a neutron-rich region to a neutron-deficient region during a peripheral collision of heavy nuclei is known as isospin diffusion, and has been previously shown to be a sensitive observable for the study of the symmetry energy at sub-saturation densities. Projectile fragmentation reactions with beams of 112,118,124Sn at 70MeV/u on targets of 112,118,124Sn have been measured at Michigan State University, in order to understand the effect of the isospin asymmetry on the reaction dynamics. Heavy fragments with Z > 20 were detected and isotopically identified using the S800 Spectrometer, and the momentum distributions of these fragments were reconstructed. Additionally, light charged particles and intermediate mass fragments were detected in an array of Si-CsI telescopes to simultaneously determine the isotopic distributions of fragments with Z < 8. The impact parameter of the collision was characterized by a measurement of the charged particle multiplicity in a 4pi scintillator array. These data provide a detailed picture of the evolution of the projectile-like residue over a range of isospin asymmetries and impact parameter. The measured yield ratios have been used to extract information about the diffusion of neutrons between the projectile and target during peripheral collisions. The validity of using isotopic yield ratios as a surrogate for the isospin asymmetry of the compound system are discussed, and the associated isospin diffusion results are presented.

  6. Premaximum observations of the type Ia SN 1990N

    NASA Technical Reports Server (NTRS)

    Leibundgut, Bruno; Kirshner, Robert P.; Filippenko, Alexei V.; Shields, Joseph C.; Foltz, Craig B.; Phillips, Mark M.; Sonneborn, George

    1991-01-01

    Spectroscopic and photometric observations of SN 1990N were obtained at ultraviolet and optical wavelengths, beginning 14 days before maximum light. The early observations reveal important differences from spectra of SN Ia's around maximum light. Photometry and spectroscopy obtained after maximum show that SN 1990N is a typical SN Ia and that most of the observed differences are due to the early epoch of the observations. The most significant characteristics are (1) the high velocities of Ca and Si up to 22,000 km/s; (2) the presence of Co and Fe 2 weeks before maximum; and (3) the more rapid increase in the UV flux compared to the optical. The most popular models for white dwarf deflagration that have provided the standard interpretation for SN Ia's at maximum light do not reproduce the high velocities of Ca II and Si II lines observed in SN 1990N.

  7. SN 2010as and Transitional Ib/c Supernovae

    NASA Astrophysics Data System (ADS)

    Folatelli, Gastón

    2014-01-01

    We present intensive photometric and spectroscopic observations of SN 2010as carried out by the Millennium Center for Supernova Studies (MCSS) and the Carnegie Supernova Project (CSP). The SN belongs to the transitional type Ibc (SN Ibc) that is characterized by the slow appearance of weak helium lines with low expansion velocities. We find a wide variety of photometric properties among otherwise spectroscopically similar SN Ibc. A hydrodynamical model is used to provide physical properties of SN 2010as in comparison with the bolometric light curve and expansion velocity.

  8. On the Sn loss from thin films of the material system Cu-Zn-Sn-S in high vacuum

    SciTech Connect

    Weber, A.; Mainz, R.; Schock, H. W.

    2010-01-15

    In this paper the Sn loss from thin films of the material system Cu-Zn-Sn-S and the subsystems Cu-Sn-S and Sn-S in high vacuum is investigated. A combination of in situ x-ray diffractometry and x-ray fluorescence (XRF) at a synchrotron light source allowed identifying phases, which tend to decompose and evaporate a Sn-containing compound. On the basis of the XRF results a quantification of the Sn loss from the films during annealing experiments is presented. It can be shown that the evaporation rate from the different phases decreases according to the order SnS{yields}Cu{sub 2}SnS{sub 3}{yields}Cu{sub 4}SnS{sub 4}{yields}Cu{sub 2}ZnSnS{sub 4}. The phase SnS is assigned as the evaporating compound. The influence of an additional inert gas component on the Sn loss and on the formation of Cu{sub 2}ZnSnS{sub 4} thin films is discussed.

  9. Electronic structure and optical property of p-type Zn-doped SnO2 with Sn vacancy

    NASA Astrophysics Data System (ADS)

    Guipeng, Sun; Jinliang, Yan; Peijiang, Niu; Delan, Meng

    2016-02-01

    The electronic structures and optical properties of intrinsic SnO2, Zn-doped SnO2, SnO2 with Sn vacancy (VSn) and Zn-doped SnO2 with Sn vacancy are explored by using first-principles calculations. Zn-doped SnO2 is a p-type semiconductor material, whose Fermi level shifts into the valence band when Zn atoms substitute Sn atoms, and the unoccupied states on the top of the valence band come from Zn 3d and O 2p states. Sn vacancies increase the relative hole number of Zn-doped SnO2, which results in a possible increase in the conductivity of Zn-doped SnO2. The Zn-doped SnO2 shows distinct visible light absorption, the increased absorption can be seen apparently with the presence of Sn vacancies in the crystal, and the blue-shift of optical spectra can be observed. Project supported by the National Natural Science Foundation of China (No. 10974077) and the Innovation Project of Shandong Graduate Education, China (No. SDYY13093).

  10. Chemical and light-stable isotope characteristics of waters from the raft river geothermal area and environs, cassia county, idaho; box elder county, Utah

    USGS Publications Warehouse

    Nathenson, M.; Nehring, N.L.; Crosthwaite, E.G.; Harmon, R.S.; Janik, C.; Borthwick, J.

    1982-01-01

    Chemical and light-stable isotope data are presented for water samples from the Raft River geothermal area and environs. On the basis of chemical character, as defined by a trilinear plot of per cent milliequivalents, and light-stable isotope data, the waters in the geothermal area can be divided into waters that have and have not mixed with cold water. The non-mixed waters have essentially a constant value of light-stable isotopes but show a large variation in chloride content. The variation of chloride composition is not the usual pattern for deep geothermal waters, where it is normally assumed that the deep water has a single chloride composition. Different mixed waters also have hot-water sources of varying chloride composition. Plots of chloride values on cross-sections show that water circulation patterns are confused, with non-mixed waters having different chloride concentrations located in close proximity. Three models can explain the characteristics of the deep geothermal water: (1) in addition to near-surface mixing of cold and hot water, there is deep mixing of two hot waters with the same enthalpy and isotopic composition but differing chloride concentrations to produce the range of chloride concentrations found in the deep geothermal water; (2) there is a single deep hot water, and the range of chloride concentrations is produced by the water passing through a zone of highly soluble materials (most likely in the sedimentary section above the basement) in which waters have different residence times or slightly different circulation paths; (3) the varying chloride concentrations in space have been caused by varying chloride concentrations in the deep feed water through time. Some of this older water has not been flushed from the system by the natural discharge. Although one model may seem more plausible than the others, the available data do not rule out any of them. Data for water samples from the Raft River and Jim Sage Mountains show that water from

  11. OBSERVATIONS OF THE M82 SN 2014J WITH THE KILODEGREE EXTREMELY LITTLE TELESCOPE

    SciTech Connect

    Siverd, Robert J.; Stassun, Keivan G.; Pepper, Joshua; Goobar, Ariel

    2015-01-20

    We report observations of the bright M82 supernova 2014J serendipitously obtained with the Kilodegree Extremely Little Telescope (KELT). The supernova (SN) was observed at high cadence for over 100 days, from pre-explosion, to early rise and peak times, through the secondary bump. The high cadence KELT data with high signal-to-noise ratio is completely unique for SN 2014J and for any other SNIa, with the exception of the (yet) unpublished Kepler data. Here, we report determinations of the SN explosion time and peak time. We also report measures of the ''smoothness'' of the light curve on timescales of minutes/hours never before probed, and we use this to place limits on energy produced from short-lived isotopes or inhomogeneities in the explosion or the circumstellar medium. From the non-observation of significant perturbations of the light curves, we derive a 3σ upper limit corresponding to 8.7 × 10{sup 36} erg  s{sup –1} for any such extra sources of luminosity at optical wavelengths.

  12. Coupling of Er light emissions to plasmon modes on In{sub 2}O{sub 3}: Sn nanoparticle sheets in the near-infrared range

    SciTech Connect

    Matsui, Hiroaki Tabata, Hitoshi; Badalawa, Wasanthamala; Nomura, Wataru; Yatsui, Takashi; Ohtsu, Motoichi; Hasebe, Takayuki; Furuta, Shinya

    2014-07-28

    Near-infrared Er photoluminescence (PL) is markedly modified using a plasmonic In{sub 2}O{sub 3}: Sn nanoparticle (NP) sheet. Modeling and optical measurements reveal the presence of different electric fields (E-field) in the NP sheet. The local E-field excited at the interface between the NP sheet and Er-emitting layer of ZnO contributes significantly towards the spectral modifications of Er PL due to matching with the photon energy of Er PL. We also determine the critical temperature for Er PL modifications, which is related to the energy transfer efficiency between Er transition dipoles in ZnO and the plasmon modes on the NP sheet.

  13. SILICON CARBIDE GRAINS OF TYPE C PROVIDE EVIDENCE FOR THE PRODUCTION OF THE UNSTABLE ISOTOPE {sup 32}Si IN SUPERNOVAE

    SciTech Connect

    Pignatari, M.; Rauscher, T.; Thielemann, F.-K.; Zinner, E.; Bertolli, M. G.; Trappitsch, R.; Hoppe, P.; Fryer, C.; Herwig, F.; Hirschi, R.; Timmes, F. X.

    2013-07-01

    Carbon-rich grains are observed to condense in the ejecta of recent core-collapse supernovae (SNe) within a year after the explosion. Silicon carbide grains of type X are C-rich grains with isotopic signatures of explosive SN nucleosynthesis have been found in primitive meteorites. Much rarer silicon carbide grains of type C are a special sub-group of SiC grains from SNe. They show peculiar abundance signatures for Si and S, isotopically heavy Si, and isotopically light S, which appear to be in disagreement with model predictions. We propose that C grains are formed mostly from C-rich stellar material exposed to lower SN shock temperatures than the more common type X grains. In this scenario, extreme {sup 32}S enrichments observed in C grains may be explained by the presence of short-lived {sup 32}Si ({tau}{sub 1/2} = 153 yr) in the ejecta, produced by neutron capture processes starting from the stable Si isotopes. No mixing from deeper Si-rich material and/or fractionation of Si from S due to molecular chemistry is needed to explain the {sup 32}S enrichments. The abundance of {sup 32}Si in the grains can provide constraints on the neutron density reached during the SN explosion in the C-rich He shell material. The impact of the large uncertainty of the neutron capture cross sections in the {sup 32}Si region is discussed.

  14. Experimental determination of the Si isotope fractionation factor between liquid metal and liquid silicate

    NASA Astrophysics Data System (ADS)

    Hin, Remco C.; Fitoussi, Caroline; Schmidt, Max W.; Bourdon, Bernard

    2014-02-01

    The conditions of core formation and the abundances of the light elements in Earth's core remain debated. Silicon isotope fractionation provides a tool contributing to this subject. We present experimentally determined Si isotope fractionation factors between liquid metal and liquid silicate at 1450 °C and 1750 °C, which allow calibrating the temperature dependence of Si isotope fractionation. Experiments were performed in a centrifuging piston cylinder at 1 GPa, employing both graphite and MgO capsules. Tin was used to lower the melting temperature of the metal alloys for experiments performed at 1450 °C. Tests reveal that neither Sn nor C significantly affects Si isotope fractionation. An alkaline fusion technique was employed to dissolve silicate as well as metal phases prior to ion exchange chemistry and mass spectrometric analysis. The results show that metal is consistently enriched in light isotopes relative to the silicate, yielding average metal-silicate fractionation factors of -1.48±0.08‰ and -1.11±0.14‰ at 1450 °C and 1750 °C, respectively. The temperature dependence of equilibrium Si isotope fractionation between metal and silicate can thus be described as Δ30SiMetal-Silicate=-4.42(±0.05)×106/T2. The Si isotope equilibrium fractionation is thus about 1.7 times smaller than previously proposed on the basis of experiments. A consequence of this smaller fractionation is that the calculated difference between the Si isotope composition of the bulk Earth and that of the bulk silicate Earth generated by core formation is smaller than previously thought. It is therefore increasingly difficult to match the Si isotope composition of the bulk silicate Earth with that of chondrites for metal-silicate equilibration temperatures above ∼2500 K. This suggests that Si isotopes were more sensitive to the early stages of core formation when low oxygen fugacities allowed significant incorporation of Si into metal.

  15. An episode of widespread ocean anoxia during the latest Ediacaran Period revealed by light U isotope compositions in carbonates

    NASA Astrophysics Data System (ADS)

    Zhang, F.

    2015-12-01

    Reconstruction of ocean redox chemistry during the Ediacaran Period is important for understanding the causal relationship between environmental oxygen levels and early metazoan evolution. Geochemical data (e.g., high Mo and U concentrations and/or heavy Mo and U isotope compositions from sedimentary rocks) provide evidence of extensive ocean oxygenation shortly after the Marinoan glaciation at ca. 632 Ma [1], during the late Ediacaran Period at ca. 560-551 Ma [2], and multiple times during the early Cambrian Period [3, 4]. These episodes of oxygenation may have been separated by intervals of less oxygenated conditions [1, 2]. However, the global redox state of the ocean during the terminal Ediacaran period (ca. 551-541 Ma) is poorly constrained. We address this knowledge gap by measuring carbonate U isotope compositions (δ238U) - a novel global ocean redox proxy - of the Gaojiashan Member of the late Ediacaran Dengying Formation (ca. 551-541 Ma) in South China. An abrupt negative shift in δ238U from values scattering around -0.45‰ to values averaging -0.95‰ (±0.20‰, 2sd) was observed in the middle Gaojiashan Member, suggesting a globally widespread expansion of ocean anoxia during the terminal Ediacaran Period. The negative δ238U shift coincides with the onset of a pronounced positive carbon isotope excursion (from 0‰ to +6‰), suggesting that ocean anoxia is the major driving force behind enhanced organic carbon burial that led to the carbon isotope excursion. The widespread anoxia recorded by the Gaojiashan Member is bracketed by known intervals of extensive ocean oxygenation, thus indicating that the Precambrian-Phanerozoic transition was characterized by oscillating ocean redox conditions. The Ediacara biota (ca. 541 Ma) [5] disappeared shortly after the widespread ocean anoxia, suggesting that an expansion of ocean anoxia may have triggerred the onset of a mass extinction in the latest Ediacaran time. References: [1] Sahoo, et al. (2012), Nature

  16. Understanding Titan's Atmospheric Isotope Inventory through Laboratory Photolysis Experiments using Vacuum Ultraviolet Photons from Advanced Light Source Synchrotron

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.

    2015-12-01

    Titan, Saturn's planet-like moon with a thick atmosphere consists mainly of N2 (98.4 %) and CH4 (1.4%). It is debated whether the N2 is primordial, or the NH3, which later converted to N2 by physic-chemical processes and, if NH3 is primordial, what is the source of that material: Saturnian-subnebula or the comets? N2 is enriched in 15N (14N/15N = 160 compared to 272 for Earth) and in geochemical terminology, d15Nair = 700 ‰ (parts per thousand with respect to ambient air). On the same scale the solar wind and Jupiter's atmosphere are ~ -400 ‰ (depleted in 15N). The comets (NH3 and HCN) and insoluble organic matter in meteorites are also enriched in 15N in the range up to a few thousand ‰. On the contrary, the carbon isotopic ratio in CH4 in Titan is similar to the other solar system bodies (12C/13C~ 89). We have performed extensive low temperature (80 K) photodissociation of N2 and CO (in presence of H2) at VUV wavelengths to measure the isotopic fractionation in the products. The integrated instantaneous fractionation in the product NH3 is about 1000 ‰ over the N2 dissociation regime (80-100 nm), which arise due to quantum mechanical selection rules. CO2 and CH4, the products of CO photodissociation, show contradictory results for two elements. While product O (trapped in CO2) is enriched by few thousand ‰, there is no significant C isotopic enrichment in CH4. These laboratory measurements along with the measurements by Cassini-Huygens spacecraft constrain the origin of volatiles in Titan's atmosphere and indicate that Titan accreted comet-like NH3 and CH4, which are the 1st generation photolysis products (of the remaining materials after the formation of gas giants) in the solar nebula. Later, NH3 converted to N2 in a bulk fashion (within Titan) and retained mostly identical isotopic composition. 15N enrichment measured in HCN in the present day atmosphere (d15Nair > 1500 ‰), is possibly from the 2nd generation N2 photolysis in Titan's modern

  17. Multi-Isotope Analysis as a Natural Reaction Probe of Biodegradation Mechanisms of 1,2- Dichloroethane

    NASA Astrophysics Data System (ADS)

    Hirschorn, S. K.; Dinglasan-Panlilio, M.; Edwards, E. A.; Lacrampe-Couloume, G.; Sherwood Lollar, B.

    2006-12-01

    1,2-Dichloroethane (1,2-DCA), a chlorinated aliphatic hydrocarbon, is an EPA priority pollutant and a widespread groundwater contaminant. Stable isotope fractionation during biodegradation of 1,2-DCA occurs due to differences in the reaction rates of heavy versus light atoms present at a reacting bond in the 1,2-DCA molecule. In general, light isotopic bonds react more quickly, producing a relative enrichment in the heavy isotope in the remaining contaminant pool. Compound specific isotope analysis has the potential to demonstrate the occurrence and extent of biodegradation at chlorinated solvent contaminated groundwater sites. In this study, stable carbon isotope fractionation was used as a novel reaction probe to provide information about the mechanism of 1,2-DCA biodegradation. Isotopic fractionation was measured during 1,2-DCA degradation by a microbial culture capable of degrading 1,2-DCA under O2-reducing and NO3-reducing conditions. The microbial culture produced isotopic enrichment values that are not only large and reproducible, but are the same whether O2 or NO3 was used as an electron acceptor. The mean isotopic enrichment value of -25.8 permil measured for the microbial culture during 1,2-DCA degradation under both O2 and NO3- reducing conditions can be converted into a kinetic isotope effect (KIE) value to relate the observed isotopic fractionation to the mechanism of degradation. This KIE value (1.05) is consistent with degradation via a hydrolysis (SN2) reaction under both electron-accepting conditions. Isotope analysis was able to provide a first line of evidence for the reaction mechanism of 1,2-DCA biodegradation by the microbial culture. Using a multi-isotope approach incorporating both carbon and hydrogen isotopic data, compound specific isotope analysis also has the potential to determine degradation mechanisms for 1,2-DCA under aerobic conditions where 1,2-DCA is known to be degraded by two distinct enzymatic pathways. Biodegradation of 1

  18. Optical properties of SnCl2 phosphor

    NASA Astrophysics Data System (ADS)

    Nara, Jun-ichi; Adachi, Sadao

    2011-04-01

    A white SnCl2 phosphor is synthesized by the chemical etching of Sn shots in an aqueous HCl solution. The optical properties of this phosphor are investigated using diffuse reflectance, photoluminescence (PL) analysis, PL excitation spectroscopy, and PL lifetime measurements. The SnCl2 phosphor exhibits PL in the blue (˜460 nm) and red spectral regions (˜600 nm) under ultraviolet excitation (≥4.1 eV). The differences in the PL features observed using Nd:YAG (λ = 266 nm) and He-Cd (λ = 325 nm) lasers as excitation light sources are interpreted using the configurational-coordinate model, taking into account the band-gap energy (˜3.8 eV) of SnCl2 and the excited-state energies of the Sn2+ ions. A reliable energy level diagram for Sn2+ ions in the SnCl2 host is also proposed.

  19. Photochemical isotope separation

    DOEpatents

    Robinson, C.P.; Jensen, R.J.; Cotter, T.P.; Greiner, N.R.; Boyer, K.

    1987-04-28

    A process is described for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium. 8 figs.

  20. Laser isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Boyer, Keith; Greiner, Norman R.

    1988-01-01

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  1. Photochemical isotope separation

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith

    1987-01-01

    A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.

  2. Laser isotope separation

    DOEpatents

    Robinson, C.P.; Reed, J.J.; Cotter, T.P.; Boyer, K.; Greiner, N.R.

    1975-11-26

    A process and apparatus for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light is described. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photolysis, photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photolysis, photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium.

  3. Oxidation of SnO to SnO{sub 2} thin films in boiling water at atmospheric pressure

    SciTech Connect

    Nose, K. Suzuki, A. Y.; Oda, N.; Kamiko, M.; Mitsuda, Y.

    2014-03-03

    We demonstrated that SnO is oxidized to SnO{sub 2} in boiling water. (001)-oriented SnO thin films were pulsed-laser deposited onto a glass substrate. The Sn valence number changed from (II) to (IV) by keeping SnO films in boiling water at atmospheric pressure for 5 h. Optical transparency of the obtained SnO{sub 2} films was greater than 95% in the visible light range. The SnO{sub 2} films possessed an amorphous structure, and exhibited dielectric properties. Atomic force microscopy and Fourier transform infrared spectroscopy revealed granular structures and the existence of –OH groups, which may account for the diffusion of oxidants within the film.

  4. Yrast isomers of ({nu}h{sub 11/2}){sup n} character in {sup 125}Sn and {sup 126}Sn

    SciTech Connect

    Zhang, C. T.; Bhattacharyya, P.; Daly, P. J.; Grabowski, Z. W.; Broda, R.; Fornal, B.; Blomqvist, J.

    2000-11-01

    Prompt and delayed {gamma}-ray coincidence measurements have located ({nu}h{sub 11/2}){sup n} yrast isomers in {sup 125}Sn and {sup 126}Sn among the products of heavy ion reactions on {sup 124}Sn targets. The decay properties of the two isomers are reported, and the results are related to those obtained for other tin isotopes in earlier works.

  5. Lighting

    SciTech Connect

    Audin, L.

    1994-12-31

    EPAct covers a vast territory beyond lighting and, like all legislation, also contains numerous {open_quotes}favors,{close_quotes} compromises, and even some sleight-of-hand. Tucked away under Title XIX, for example, is an increase from 20% to 28% tax on gambling winnings, effective January 1, 1993 - apparently as a way to help pay for new spending listed elsewhere in the bill. Overall, it is a landmark piece of legislation, about a decade overdue. It remains to be seen how the Federal Government will enforce upgrading of state (or even their own) energy codes. There is no mention of funding for {open_quotes}energy police{close_quotes} in EPAct. Merely creating such a national standard, however, provides a target for those who sincerely wish to create an energy-efficient future.

  6. Fabrication of cubic Zn2SnO4/SnO2 complex hollow structures and their sunlight-driven photocatalytic activity.

    PubMed

    Sun, Linqiang; Han, Xiao; Jiang, Zhe; Ye, Tingting; Li, Rong; Zhao, Xinsheng; Han, Xiguang

    2016-06-30

    Uniform hollow, yolk-shell and double-shell Zn2SnO4/SnO2 nanoparticles with cubic morphologies have been synthesized using "etching-second growth-annealed" methods. Due to the high light-harvesting efficiency and low recombination rate of the photo-generated electron-hole pair, double-shell structures of Zn2SnO4/SnO2 nanoparticles show an obvious improvement in photocatalytic activity. PMID:26912088

  7. Dirac neutrinos and SN 1987A

    NASA Technical Reports Server (NTRS)

    Turner, Michael S.

    1991-01-01

    Previous work has shown that the cooling of SN 1987A excludes a Dirac-neutrino mass greater than theta(20 keV) for nu(sub e), nu(sub mu), or nu(sub tau). The emission of wrong-helicity, Dirac neutrinos from SN 1987A, is re-examined. It is concluded that the effect of a Dirac neutrino on the cooling of SN 1987A has been underestimated due to neutrino degeneracy and additional emission processes. The limit that follows from the cooling of SN 1987A is believed to be greater (probably much greater) than 10 keV. This result is significant in light of the recent evidence for a 17 keV mass eigenstate that mixes with the electron neutrino.

  8. Large-scale solid-state synthesis of Sn-SnO2 nanoparticles from layered SnO by sunlight: a material for dye degradation in water by photocatalytic reaction.

    PubMed

    Sinha, Arun Kumar; Pradhan, Mukul; Sarkar, Sougata; Pal, Tarasankar

    2013-03-01

    Phase pure spherical Sn-SnO2 nanoparticles (∼ 50 nm) in gram level have been synthesized from well-defined SnO microplates (∼ 2.0 μm) using focused solar irradiation. The first step of the reaction involves simple stirring of a strong NaOH solution with fine SnCl2·2H2O powder. Precipitated blue black microplates of SnO are finally transformed into high band gap Sn-SnO2 nanoparticles with sunlight. During the solid-state photodecomposition of microplates, spherical SnO2 nanoparticles along with tiny Sn(0) particles are evolved simultaneously. Tiny Sn(0) particles, improved surface area, stability toward adverse environmental conditions, and inherited negative surface charge electrostatically stabilize the Sn-SnO2 particle rendering it excellent water dispersible. The presence of Sn(0) nanoparticles in spherical SnO2 nanoparticles improves the charge (electrons and holes) separation efficiency. Then, the as-prepared particles selectively invite cationic dye molecules to the particle surface due to negative surface charge and degrade the dyes at a faster rate under UV light. PMID:23409805

  9. Spectrum synthesis of the Type Ia supernovae SN 1992A and SN 1981B

    NASA Technical Reports Server (NTRS)

    Nugent, Peter; Baron, E.; Hauschildt, Peter H.; Branch, David

    1995-01-01

    We present non-local thermodynamic equilibrium (non-LTE) synthetic spectra for the Type Ia supernovae SN 1992A and SN 1981B, near maximum light. At this epoch both supernovae were observed from the UV through the optical. This wide spectral coverage is essential for determining the density structure of a SN Ia. Our fits are in good agreement with observation and provide some insight as to the differences between these supernovae. We also discuss the application of the expanding photosphere method to SNe Ia which gives a distance that is independent of those based on the decay of Ni-56 and Cepheid variable stars.

  10. SN 1604 in China

    NASA Astrophysics Data System (ADS)

    Wang, Z. R.; Zhao, Y.; Li, M.; Zhou, Q. L.

    2005-06-01

    The 6th East Asian Meeting of Astronomy was held just at the time of 400 years after the discovery of SN (supernova) 1604 and its pre-maximum observation by the astronomers both from the East and the West in the 17th century. It has a special meaning and is interesting to look back on the historical observation of SN 1604. In this paper, we only limit to concern the Chinese observation on SN 1604.

  11. Photometric Monitoring of SN 2011dh

    NASA Astrophysics Data System (ADS)

    Spencer, Michelle E.; Joner, M. D.; Laney, C. D.; Stoker, E.

    2012-01-01

    We present BVRI light curves of SN 2011dh located in the nearby, nearly face-on spiral galaxy M51. The data were secured using the 0.9 m telescope at the West Mountain Observatory. The data span approximately 100 days with the first observations being before maximum light. The shapes of the light curves are well defined and the time of maximum light is well established. Standard Johnson-Cousins filters were utilized for all of the observations and several nights from this data set were standardized using selections of Landolt standards. SN 2011dh has been classified as Type IIb core-collapse supernova. We would like to thank the Brigham Young University College of Physical and Mathematical Sciences for continued support of mentored student research at the West Mountain Observatory. Partial support for this project was derived from NSF grant AST #0618209.

  12. Band structure in 113Sn

    NASA Astrophysics Data System (ADS)

    Banerjee, P.; Ganguly, S.; Pradhan, M. K.; Sharma, H. P.; Muralithar, S.; Singh, R. P.; Bhowmik, R. K.

    2016-07-01

    The structure of collective bands in 113Sn, populated in the reaction 100Mo(19F,p 5 n ) at a beam energy of 105 MeV, has been studied. A new positive-parity sequence of eight states extending up to 7764.9 keV and spin (39 /2+) has been observed. The band is explained as arising from the coupling of the odd valence neutron in the g7 /2 or the d5 /2 orbital to the deformed 2p-2h proton configuration of the neighboring even-A Sn isotope. Lifetimes of six states up to an excitation energy of 9934.9 keV and spin 47 /2-belonging to a Δ I =2 intruder band have been measured for the first time, including an upper limit for the last state, from Doppler-shift-attenuation data. A moderate average quadrupole deformation β2=0.22 ±0.02 is deduced from these results for the five states up to spin 43 /2- . The transition quadrupole moments decrease with increase in rotational frequency, indicating a reduction of collectivity with spin, a feature common for terminating bands. The behavior of the kinematic and dynamic moments of inertia as a function of rotational frequency has been studied and total Routhian surface calculations have been performed in an attempt to obtain an insight into the nature of the states near termination.

  13. SN 1991bg - A type Ia supernova with a difference

    NASA Technical Reports Server (NTRS)

    Leibundgut, Bruno; Kirshner, Robert P.; Phillips, Mark M.; Wells, Lisa A.; Suntzeff, N. B.; Hamuy, Mario; Schommer, R. A.; Walker, A. R.; Gonzalez, L.; Ugarte, P.

    1993-01-01

    While SN 1991bg is an unusual type Ia SN in such a feature as the brief duration of the photospheric phase, which ended only two weeks after maximum, it shares with other Ia SNs strong Si II and Ca II lines near maximum light. In addition, the light and color curve slopes are almost identical with the templates at late times. The spectral evolution of SN 1991bg is also unique but not unrecognizable; nevertheless, the peculiarities associated with this event complicate the fundamental question as to whether the Ia SNs make good standard candles.

  14. Stellar neutron capture cross sections of the tin isotopes

    SciTech Connect

    Wisshak, K.; Voss, F.; Theis, C.; Kaeppeler, F.; Guber, K.; Kazakov, L.; Kornilov, N.; Reffo, G.

    1996-09-01

    The neutron capture cross sections of {sup 114}Sn, {sup 115}Sn, {sup 116}Sn, {sup 117}Sn, {sup 118}Sn, and {sup 120}Sn were measured in the energy range from 3 to 225 keV at the Karlsruhe 3.75 MV Van de Graaff accelerator. Neutrons were produced via the {sup 7}Li({ital p},{ital n}){sup 7}Be reaction using a pulsed proton beam. Capture events were registered with the Karlsruhe 4{pi} barium fluoride detector. The experiment was complicated by the small ({ital n},{gamma}) cross sections of the proton magic tin isotopes and by the comparably low enrichment of the rare isotopes {sup 114}Sn and {sup 115}Sn. Despite significant corrections for capture of scattered neutrons and for isotopic impurities, the high efficiency and the spectroscopic quality of the BaF{sub 2} detector allowed the determination of the cross-section ratios with overall uncertainties of 1{endash}2{percent}, five times smaller compared to existing data. Based on these results, Maxwellian averaged ({ital n},{gamma}) cross sections were calculated for thermal energies between {ital kT}=10 and 100 keV. These data are used for a discussion of the solar tin abundance and for an improved determination of the isotopic {ital s}- and {ital r}-process components. {copyright} {ital 1996 The American Physical Society.}

  15. NEUTRON-RICH CHROMIUM ISOTOPE ANOMALIES IN SUPERNOVA NANOPARTICLES

    SciTech Connect

    Dauphas, N.; Remusat, L.; Papanastassiou, D. A.; Guan, Y.; Ma, C.; Eiler, J. M.; Chen, J. H.; Roskosz, M.; Stodolna, J.

    2010-09-10

    Neutron-rich isotopes with masses near that of iron are produced in Type Ia and II supernovae (SNeIa and SNeII). Traces of such nucleosynthesis are found in primitive meteorites in the form of variations in the isotopic abundance of {sup 54}Cr, the most neutron-rich stable isotope of chromium. The hosts of these isotopic anomalies must be presolar grains that condensed in the outflows of SNe, offering the opportunity to study the nucleosynthesis of iron-peak nuclei in ways that complement spectroscopic observations and can inform models of stellar evolution. However, despite almost two decades of extensive search, the carrier of {sup 54}Cr anomalies is still unknown, presumably because it is fine grained and is chemically labile. Here, we identify in the primitive meteorite Orgueil the carrier of {sup 54}Cr anomalies as nanoparticles (<100 nm), most likely spinels that show large enrichments in {sup 54}Cr relative to solar composition ({sup 54}Cr/{sup 52}Cr ratio >3.6 x solar). Such large enrichments in {sup 54}Cr can only be produced in SNe. The mineralogy of the grains supports condensation in the O/Ne-O/C zones of an SNII, although a Type Ia origin cannot be excluded. We suggest that planetary materials incorporated different amounts of these nanoparticles, possibly due to late injection by a nearby SN that also delivered {sup 26}Al and {sup 60}Fe to the solar system. This idea explains why the relative abundance of {sup 54}Cr and other neutron-rich isotopes vary between planets and meteorites. We anticipate that future isotopic studies of the grains identified here will shed new light on the birth of the solar system and the conditions in SNe.

  16. Particle and light fragment emission in peripheral heavy ion collisions at Fermi energies

    SciTech Connect

    Piantelli, S.; Maurenzig, P. R.; Olmi, A.; Bardelli, L.; Bartoli, A.; Bini, M.; Casini, G.; Coppi, C.; Mangiarotti, A.; Pasquali, G.; Poggi, G.; Stefanini, A. A.; Taccetti, N.; Vanzi, E.

    2006-09-15

    A systematic investigation of the average multiplicities of light charged particles and intermediate mass fragments emitted in peripheral and semiperipheral collisions is presented as a function of the beam energy, violence of the collision, and mass of the system. The data have been collected with the FIASCO setup in the reactions {sup 93}Nb+{sup 93}Nb at (17,23,30,38)A MeV and {sup 116}Sn+{sup 116}Sn at (30,38)A MeV. The midvelocity emission has been separated from the emission of the projectile-like fragment. This last component appears to be compatible with an evaporation from an equilibrated source at normal density, as described by the statistical code GEMINI at the appropriate excitation energy. On the contrary, the midvelocity emission presents remarkable differences in both the dependence of the multiplicities on the energy deposited in the midvelocity region and the isotopic composition of the emitted light charged particles.

  17. Precision mass measurements beyond 132Sn: anomalous behavior of odd-even staggering of binding energies.

    PubMed

    Hakala, J; Dobaczewski, J; Gorelov, D; Eronen, T; Jokinen, A; Kankainen, A; Kolhinen, V S; Kortelainen, M; Moore, I D; Penttilä, H; Rinta-Antila, S; Rissanen, J; Saastamoinen, A; Sonnenschein, V; Äystö, J

    2012-07-20

    Atomic masses of the neutron-rich isotopes (121-128)Cd, (129,131)In, (130-135)Sn, (131-136)Sb, and (132-140)Te have been measured with high precision (10 ppb) using the Penning-trap mass spectrometer JYFLTRAP. Among these, the masses of four r-process nuclei (135)Sn, (136)Sb, and (139,140)Te were measured for the first time. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across N = 82 for Sn, with a Z dependence that is unexplainable by the current theoretical models. PMID:22861839

  18. Cosmology: Rare isotopic insight into the Universe

    NASA Astrophysics Data System (ADS)

    Prantzos, Nikos

    2016-01-01

    Light isotopes of hydrogen and helium formed minutes after the Big Bang. The study of one of these primordial isotopes, helium-3, has now been proposed as a useful strategy for constraining the physics of the standard cosmological model.

  19. Dynamic Nuclear Polarization NMR Enables the Analysis of Sn-Beta Zeolite Prepared with Natural Abundance 119Sn Precursors

    PubMed Central

    2015-01-01

    The catalytic activity of tin-containing zeolites, such as Sn-Beta, is critically dependent on the successful incorporation of the tin metal center into the zeolite framework. However, synchrotron-based techniques or solid-state nuclear magnetic resonance (ssNMR) of samples enriched with 119Sn isotopes are the only reliable methods to verify framework incorporation. This work demonstrates, for the first time, the use of dynamic nuclear polarization (DNP) NMR for characterizing zeolites containing ∼2 wt % of natural abundance Sn without the need for 119Sn isotopic enrichment. The biradicals TOTAPOL, bTbK, bCTbK, and SPIROPOL functioned effectively as polarizing sources, and the solvent enabled proper transfer of spin polarization from the radical’s unpaired electrons to the target nuclei. Using bCTbK led to an enhancement (ε) of 75, allowing the characterization of natural-abundance 119Sn-Beta with excellent signal-to-noise ratios in <24 h. Without DNP, no 119Sn resonances were detected after 10 days of continuous analysis. PMID:24697321

  20. Beta-Decay Studies near 100Sn

    SciTech Connect

    Karny, M.; Batist, L.; Banu, A.; Becker, F.; Blazhev, A.; Burkard, K.; Bruchle, W.; Doring, J.; Faestermann, T.; Gorska, M.; Grawe, H.; Janas, Z.; Jungclaus, A.; Kavatsyuk, M.; Kavatsyuk, O.; Kirchner, R.; La Commara, M.; Mandal, S.; Mazzocchi, C.; Miernik, K.; Mukha, I.; Muralithar, S.; Plettner, C.; Plochocki, A.; Roeckl, E.; Romoli, M.; Rykaczewski, Krzysztof Piotr; Schadel, M.; Schmidt, K.; Schwengner, R.; Zylicz, J.

    2005-01-01

    The {beta}-decay of {sup 102}Sn was studied by using high-resolution germanium detectors as well as a Total Absorption Spectrometer (TAS). A decay scheme has been constructed based on the {gamma}-{gamma} coincidence data. The total experimental Gamow-Teller strength B{sub GT}{sup exp} of {sup 102}Sn was deduced from the TAS data to be 4.2(9). A search for {beta}-delayed {gamma}-rays of {sup 100}Sn decay remained unsuccessful. However, a Gamow-Teller hindrance factor h = 2.2(3), and a cross-section of about 3nb for the production of {sup 100}Sn in fusion-evaporation reaction between {sup 58}Ni beam and {sup 50}Cr target have been estimated from the data on heavier tin isotopes. The estimated hindrance factor is similar to the values derived for lower shell nuclei.

  1. Quantitative Determination of Isotope Ratios from Experimental Isotopic Distributions

    PubMed Central

    Kaur, Parminder; O’Connor, Peter B.

    2008-01-01

    Isotope variability due to natural processes provides important information for studying a variety of complex natural phenomena from the origins of a particular sample to the traces of biochemical reaction mechanisms. These measurements require high-precision determination of isotope ratios of a particular element involved. Isotope Ratio Mass Spectrometers (IRMS) are widely employed tools for such a high-precision analysis, which have some limitations. This work aims at overcoming the limitations inherent to IRMS by estimating the elemental isotopic abundance from the experimental isotopic distribution. In particular, a computational method has been derived which allows the calculation of 13C/12C ratios from the whole isotopic distributions, given certain caveats, and these calculations are applied to several cases to demonstrate their utility. The limitations of the method in terms of the required number of ions and S/N ratio are discussed. For high-precision estimates of the isotope ratios, this method requires very precise measurement of the experimental isotopic distribution abundances, free from any artifacts introduced by noise, sample heterogeneity, or other experimental sources. PMID:17263354

  2. SN1987A's Twentieth Anniversary

    NASA Astrophysics Data System (ADS)

    2007-02-01

    Looking back at 20 Years of Observations of this Supernova with ESO telescopes The unique supernova SN 1987A has been a bonanza for astrophysicists. It provided several observational 'firsts,' like the detection of neutrinos from an exploding star, the observation of the progenitor star on archival photographic plates, the signatures of a non-spherical explosion, the direct observation of the radioactive elements produced during the blast, observation of the formation of dust in the supernova, as well as the detection of circumstellar and interstellar material. ESO PR Photo 08a/07 ESO PR Photo 08a/07 SN1987A in the Large Magellanic Cloud Today, it is exactly twenty years since the explosion of Supernova 1987A in the Large Magellanic Cloud was first observed, at a distance of 163,000 light-years. It was the first naked-eye supernova to be seen for 383 years. Few events in modern astronomy have met with such an enthusiastic response by the scientists and now, after 20 years, it continues to be an extremely exciting object that is further studied by astronomers around the world, in particular using ESO's telescopes. When the first signs of Supernova 1987A, the first supernova of the year 1987, were noticed early on 24 February of that year, it was clear that this would be an unusual event. It was discovered by naked-eye and on a panoramic photographic plate taken with a 10-inch astrograph on Las Campanas in Chile by Oscar Duhalde and Ian Shelton, respectively. A few hours earlier, still on 23 February, two large underground detectors - in Japan and the USA - had registered the passage of high-energy neutrinos. Since SN 1987A exploded in the Large Magellanic Cloud (LMC), it was only accessible to telescopes in the Southern Hemisphere, more particularly in Australia, South Africa, and South America. In Chile, ESO's observatory at La Silla with its armada of telescopes with sizes between 0.5 and 3.6-m, played an important role. ESO PR Photo 08c/07 ESO PR Photo 08c/07 The

  3. Temperature varying photoconductivity of GeSn alloys grown by chemical vapor deposition with Sn concentrations from 4% to 11%

    NASA Astrophysics Data System (ADS)

    Hart, John; Adam, Thomas; Kim, Yihwan; Huang, Yi-Chiau; Reznicek, Alexander; Hazbun, Ramsey; Gupta, Jay; Kolodzey, James

    2016-03-01

    Pseudomorphic GeSn layers with Sn atomic percentages between 4.5% and 11.3% were grown by chemical vapor deposition using digermane and SnCl4 precursors on Ge virtual substrates grown on Si. The layers were characterized by x-ray diffraction rocking curves and reciprocal space maps. Photoconductive devices were fabricated, and the dark current was found to increase with Sn concentration. The responsivity of the photoconductors was measured at a wavelength of 1.55 μm using calibrated laser illumination at room temperature and a maximum value of 2.7 mA/W was measured for a 4.5% Sn device. Moreover, the responsivity for higher Sn concentration was found to increase with decreasing temperature. Spectral photoconductivity was measured using Fourier transform infrared spectroscopy. The photoconductive absorption edge continually increased in wavelength with increasing tin percentage, out to approximately 2.4 μm for an 11.3% Sn device. The direct band gap was extracted using Tauc plots and was fit to a bandgap model accounting for layer strain and Sn concentration. This direct bandgap was attributed to absorption from the heavy-hole band to the conduction band. Higher energy absorption was also observed, which was thought to be likely from absorption in the light-hole band. The band gaps for these alloys were plotted as a function of temperature. These experiments show the promise of GeSn alloys for CMOS compatible short wave infrared detectors.

  4. Isotopic Biogeochemistry

    NASA Technical Reports Server (NTRS)

    Hayes, J. M.

    1985-01-01

    An overview is provided of the biogeochemical research. The funding, productivity, personnel and facilities are reviewed. Some of the technical areas covered are: carbon isotopic records; isotopic studies of banded iron formations; isotope effects in microbial systems; studies of organic compounds in ancient sediments; and development in isotopic geochemistry and analysis.

  5. Measurement of the Abundance of Radioactive Be-10 and Other Light Isotopes in Cosmic Radiation Up to 2 GeV /Nucleon with the Balloon-Borne Instrument Isomax

    NASA Technical Reports Server (NTRS)

    Hams, T.; Barbier, L. M.; Bremerich, M.; Christian, E. R.; deNolfo, G. A.; Geier, S.; Goebel, H.; Gupta, S. K.; Hof, M.; Menn, W.

    2004-01-01

    The Isotope Magnet Experiment (ISOMAX), a balloon-borne superconducting magnet spectrometer, was designed to measure the isotopic composition of the light isotopes (3 les than or = Z less than or = 8) of cosmic radiation up to 4 GeV/nucleon with a mass resolution of better than 0.25 amu by using the velocity versus rigidity technique. To achieve this stringent mass resolution, ISOMAX was composed of three major detector systems: a magnetic rigidity spectrometer with a precision drift chamber tracker in conjunction with a three-layer time-of-flight system, and two silica-aerogel Cerenkov counters for velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive Be-10 with respect to its stable neighbor isotope Be-9, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on 1998 August 4-5 from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g/sq cm. The isotopic ratio at the top of the atmosphere for Be-10/Be-9 was measured to be 0.195 +/- 0.036 (statistical) +/- 0.039 (systematic) between 0.26 and 1.03 GeV/nucleon and 0.317 +/- 0.109(statistical) +/- 0.042(systematic) between 1.13 and 2.03 GeV/nucleon. This is the first measurement of its kind above l GeV/nucleon. ISOMAX results tend to be higher than predictions from current propagation models. In addition to the beryllium results, we report the isotopic ratios of neighboring lithium and boron in the energy range of the time-of-flight system (up to approx. 1 GeV/nucleon). The lithium and boron ratios agree well with existing data and model predictions at similar energies.

  6. Method for isotope separation by photodeflection

    DOEpatents

    Bernhardt, Anthony F.

    1977-01-01

    In the method of separating isotopes wherein a desired isotope species is selectively deflected out of a beam of mixed isotopes by irradiating the beam with a directed beam of light of narrowly defined frequency which is selectively absorbed by the desired species, the improvement comprising irradiating the deflected beam with light from other light sources whose frequencies are selected to cause the depopulation of any metastable excited states.

  7. Hydrogen peroxide route to Sn-doped titania photocatalysts

    PubMed Central

    2012-01-01

    Background The work aims at improving photocatalytic activity of titania under Vis light irradiation using modification by Sn ions and an original, simple synthesis method. Tin-doped titania catalysts were prepared by thermal hydrolysis of aqueous solutions of titanium peroxo-complexes in the presence of SnCl4 or SnCl2 using an original, proprietary "one pot" synthesis not employing organic solvents, metallo-organic precursors, autoclave aging nor post-synthesis calcination. The products were characterized in details by powder diffraction, XPS, UV–vis, IR, and Raman spectroscopies, electron microscopy and surface area and porosity measurements Results The presence of tin in synthesis mixtures favors the formation of rutile and brookite at the expense of anatase, decreases the particle size of all formed titania polymorphs, and extends light absorption of titania to visible light region >400 nm by both red shift of the absorption edge and introduction of new chromophores. The photocatalytic activity of titania under UV irradiation and >400 nm light was tested by decomposition kinetics of Orange II dye in aqueous solution Conclusions Doping by Sn improves titania photoactivity under UV light and affords considerable photoactivity under >400 nm light due to increased specific surface area and a phase heterogeneity of the Sn-doped titania powders. PMID:23035821

  8. Isotope separation by laser means

    DOEpatents

    Robinson, C. Paul; Jensen, Reed J.; Cotter, Theodore P.; Greiner, Norman R.; Boyer, Keith

    1982-06-15

    A process for separating isotopes by selective excitation of isotopic species of a volatile compound by tuned laser light. A highly cooled gas of the volatile compound is produced in which the isotopic shift is sharpened and defined. Before substantial condensation occurs, the cooled gas is irradiated with laser light precisely tuned to a desired wavelength to selectively excite a particular isotopic species in the cooled gas. The laser light may impart sufficient energy to the excited species to cause it to undergo photochemical reaction or even to photoionize. Alternatively, a two-photon irradiation may be applied to the cooled gas to induce photochemical reaction or photoionization. The process is particularly applicable to the separation of isotopes of uranium and plutonium.

  9. Combination of the (87)Sr/(86)Sr ratio and light stable isotopic values (δ(13)C, δ(15)N and δD) for identifying the geographical origin of winter wheat in China.

    PubMed

    Liu, Hongyan; Wei, Yimin; Lu, Hai; Wei, Shuai; Jiang, Tao; Zhang, Yingquan; Guo, Boli

    2016-12-01

    This study aims to investigate whether isotopic signatures can be used to develop reliable fingerprints for discriminating the geographical origin of Chinese winter wheat, and to evaluate the discrimination effects of δ(13)C, δ(15)N and δD, alone or with (87)Sr/(86)Sr. In this study, the values of δ(13)C, δ(15)N and δD, and the (87)Sr/(86)Sr ratios of wheat and provenance soils from three regions were determined. Significant differences were found in all parameters of wheat and (87)Sr/(86)Sr in soil extract (reflecting the bioavailable fraction of soil) among different regions. A significantly positive correlation was observed between the (87)Sr/(86)Sr ratios of wheat and soil extracts. An overall correct classification rate of 77.8% was obtained for discriminating wheat from three regions based on light stable isotopes (δ(13)C, δ(15)N, and δD). The correct classification rate of 98.1% could be obtained with the combination of the (87)Sr/(86)Sr ratio and the light stable isotopic values. PMID:27374544

  10. SN 2004aw: confirming diversity of Type Ic supernovae

    NASA Astrophysics Data System (ADS)

    Taubenberger, S.; Pastorello, A.; Mazzali, P. A.; Valenti, S.; Pignata, G.; Sauer, D. N.; Arbey, A.; Bärnbantner, O.; Benetti, S.; Della Valle, A.; Deng, J.; Elias-Rosa, N.; Filippenko, A. V.; Foley, R. J.; Goobar, A.; Kotak, R.; Li, W.; Meikle, P.; Mendez, J.; Patat, F.; Pian, E.; Ries, C.; Ruiz-Lapuente, P.; Salvo, M.; Stanishev, V.; Turatto, M.; Hillebrandt, W.

    2006-09-01

    Optical and near-infrared (near-IR) observations of the Type Ic supernova (SN Ic) 2004aw are presented, obtained from -3 to +413 d with respect to the B-band maximum. The photometric evolution is characterized by a comparatively slow post-maximum decline of the light curves. The peaks in redder bands are significantly delayed relative to the bluer bands, the I-band maximum occurring 8.4 d later than that in B. With an absolute peak magnitude of -18.02 in the V band the SN can be considered fairly bright, but not exceptional. This also holds for the U through I bolometric light curve, where SN 2004aw has a position intermediate between SNe 2002ap and 1998bw. Spectroscopically SN 2004aw provides a link between a normal SN Ic like SN 1994I and the group of broad-lined SNe Ic. The spectral evolution is rather slow, with a spectrum at day +64 being still predominantly photospheric. The shape of the nebular [OI] λλ6300, 6364 line indicates a highly aspherical explosion. Helium cannot be unambiguously identified in the spectra, even in the near-IR. Using an analytical description of the light-curve peak we find that the total mass of the ejecta in SN 2004aw is 3.5-8.0Msolar, significantly larger than that in SN 1994I, although not as large as in SN 1998bw. The same model suggests that about 0.3Msolar of 56Ni has been synthesized in the explosion. No connection to a GRB can be firmly established. Based on observations at ESO-Paranal, Prog. 074.D-0161(A). E-mail: tauben@mpa-garching.mpg.de

  11. Different Complexation Behavior of P-Functionalized Ferrocene Derivatives Towards SnCl2 , SnCl4 and SnPh2 Cl2 : Auto-ionization and Redox-Type Reactions.

    PubMed

    Gawron, Matthias; Dietz, Christina; Lutter, Michael; Duthie, Andrew; Jouikov, Viatcheslav; Jurkschat, Klaus

    2015-11-01

    The novel phosphonyl-substituted ferrocene derivatives [Fe(η(5) -Cp)(η(5) -C5 H3 {P(O)(O-iPr)2 }2 -1,2)] (Fc(1,2) ) and [Fe{η(5) -C5 H4 P(O)(O-iPr)2 }2 ] (Fc(1,1') ) react with SnCl2 , SnCl4 , and SnPh2 Cl2 , giving the corresponding complexes [(Fc(1,2) )2 SnCl][SnCl3 ] (1), [{(Fc(1,1') )SnCl2 }n ] (2), [(Fc(1,1') )SnCl4 ] (3), [{(Fc(1,1') )SnPh2 Cl2 }n ] (4), and [(Fc(1,2) )SnCl4 ] (5), respectively. The compounds are characterized by elemental analyses, (1) H, (13) C, (31) P, (119) Sn NMR and IR spectroscopy, (31) P and (119) Sn CP-MAS NMR spectroscopy, cyclovoltammetry, electrospray ionization mass spectrometry, and single-crystal as well as powder X-ray diffraction analyses. The experimental work is accompanied by DFT calculations, which help to shed light on the origin for the different reaction behavior of Fc(1,1') and Fc(1,2) towards tin(II) chloride. PMID:26480839

  12. Synthesis and Photoluminescence Properties of SnO2 Nanopowder

    NASA Astrophysics Data System (ADS)

    Arai, Takahiro; Adachi, Sadao

    2012-10-01

    SnO2 nanopowder was synthesized by calcining metastannic salt (SnO2·H2O) prepared by chemically etching metallic Sn in aqueous HNO3 solution. The calcined SnO2 nanopowder was investigated by X-ray diffraction (XRD) measurement and photoluminescence (PL) spectroscopy. The XRD and PL intensities increased with increasing calcining temperature, yielding an activation energy of ˜0.65 eV. The PL spectra of the calcined SnO2 nanopowder exhibited green (G) and red (R) emission bands with peaks at ˜2.5 and ˜2.0 eV, respectively, that were clearly dependent not only on the excitation light wavelength but also on the sample temperature. The temperature dependence of the PL intensity between 20 and 300 K was explained by the thermal quenching with activation energies of ˜15 meV (T=20-60 K) and ˜0.12-0.18 eV (T ≥100 K). The G and R emission states were found to originate from the Jahn-Teller effect of the 5s2 (Sn2+) ions in the SnO2 matrix and were similar to those generally observed in many ns2-doped alkali halides and SnCl2.

  13. Synthesis and photocatalytic study of SnO2/Zn2SnO4 nanocomposite prepared by sol-gel method using single source molecular precursor

    NASA Astrophysics Data System (ADS)

    Ullah, Hameed; Khatoon, Asma; Akhtar, Zareen

    2014-12-01

    A single-source molecular precursor (SSP), ([Cl2Sn(μ-OtBu)2ZnCl2(bpy)]), was designed, developed, and subsequently used in a sol-gel process for the synthesis of SnO2/Zn2SnO4 nanocomposite at pH 9 adjusted by using a NaOH solution. The pre- and post-sintering IR spectra revealed the presence and absence, respectively, of the OH group. The powder XRD confirms the formation of the single crystalline ZnSn(OH)6 phase before sintering. However, the sintered product is composed of coupled oxides, i.e. the binary SnO2 and ternary Zn2SnO4. The scanning electron microscope (SEM) images taken after sonicating the SnO2/Zn2SnO4 powder show the macroporous texture of the powder. The uniformly sized particles are in two different morphological forms, i.e. cubic and spherical. The energy-dispersive x-ray (EDX) spectroscopy confirms the elemental composition of the SnO2/Zn2SnO4 nanocomposite (Zn:Sn:O = 2:2:6). The photocatalytic efficiency of the SnO2/Zn2SnO4 nanocomposite was tested by using the dye Sudan Red B a colorant used in red chilies. More than 82% of the dye degraded after 120 min of exposure to the UV light. The efficient photocatalytic activity is attributed to the better electron/hole pair separation which resulted from the coupling of Zn2SnO4 and SnO2 at the molecular level and produced efficient grain boundary interfaces.

  14. Supernova mechanisms: Before and after SN1987a

    SciTech Connect

    Kahana, S.H.

    1987-01-01

    The impact of SN1987a on theoretical studies of the specific mechanism generating Type II supernovae is examined. The explosion energy extracted from analysis of the light curve for SN 1987a is on the edge of distinguishing between a prompt explosion from a hydrodynamic shock and a delayed, neutrino-induced, explosion. The detection of neutrinos from 1987a is also reanalyzed. 30 refs., 2 tabs.

  15. Precisely Controlled Synthesis of High Quality Kesterite Cu2ZnSnS4 Thin Film via Co-Electrodeposited CuZnSn Alloy Film.

    PubMed

    Hreid, Tubshin; Tiong, Vincent Tiing; Cai, Molang; Wang, Hongxia; Will, Geoffrey

    2016-06-01

    In this work, a facile co-electrodeposition method was used to fabricate CuZnSn alloy films where the content of copper, zinc and tin could be precisely controlled through manipulating the mass transfer process in the electrochemical deposition. By finely tuning the concentration of the cations of Cu2+, Zn2+ and Sn2+ in the electrochemical bath solution, uniform CuZnSn film with desired composition of copper poor and zinc rich was made. Sulphurisation of the CuZnSn alloy film led to the formation of compact and large grains Cu2ZnSnS4 thin film absorber with an optimum composition of Cu/(Zn+Sn) ≈ 0.8, Zn/Sn ≈ 1.2. Both SEM morphology and EDS mapping results confirmed the uniformity of the CuZnSn and Cu2ZnSnS4 films and the homogeneous distribution of Cu, Zn, Sn and S elements in the bulk films. The XRD and Raman measurements indicated that the synthesized Cu2ZnSnS4 film was kesterite phase without impurities detected. Photoelectrochemical tests were carried out to evaluate the CZTS film's photocurrent response under illumination of green light. PMID:27427618

  16. Early Results from the DES SN Survey

    NASA Astrophysics Data System (ADS)

    Scolnic, Daniel; Dark Energy Survey

    2016-01-01

    The Dark Energy Survey Supernova program (DES SN) has already discovered over 1000 Type Ia supernovae with well-sampled multi-color light curves in the redshift range 0.1 < z < 1.2. I will present an overview of the survey and show recent advances in our detection, photometry, calibration and spectroscopic follow-up pipelines. I will go over initial results from photometric classification of our sample and discuss methods used to reach measurements of cosmological parameters.

  17. Spectroscopic observations and analysis of the peculiar SN1999aa

    SciTech Connect

    Garavini, G.; Folatelli, G.; Goobar, A.; Nobili, S.; Aldering,G.; Amadon, A.; Amanullah, R.; Astier, P.; Balland, C.; Blanc, G.; Burns,M.S.; Conley, A.; Dahlen, T.; Deustua, S.E.; Ellis, R.; Fabbro, S.; Fan,X.; Frye, B.; Gates, E.L.; Gibbons, R.; Goldhaber, G.; Goldman, B.; Groom, D.E.; Haissinski, J.; Hardin, D.; Hook, I.M.; Howell, D.A.; Kasen,D.; Kent, S.; Kim, A.G.; Knop, R.A.; Lee, B.C.; Lidman, C.; Mendez, J.; Miller, G.J.; Moniez, M.; Mourao, A.; Newberg, H.; Nugent, P.E.; Pain,R.; Perdereau, O.; Perlmutter, S.; Prasad, V.; Quimby, R.; Raux, J.; Regnault, N.; Rich, J.; Richards, G.T.; Ruiz-Lapuente, P.; Sainton, G.; Schaefer, B.E.; Schahmaneche, K.; Smith, E.; Spadafora, A.L.; Stanishev,V.; Walton, N.A.; Wang, L.; Wood-Vasey, W.M.

    2003-12-10

    We present an extensive new time series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Our data set includes 25 optical spectra between -11 and +58 days with respect to B-band maximum light, providing an unusually complete time history. The early spectra resemble those of an SN 1991T-like object but with a relatively strong CaH and K absorption feature. The first clear sign of Si II lambda 6355, characteristic of Type Ia supernovae, is found at day -7, and its velocity remains constant up to at least the first month after B-band maximum light. The transition to normal-looking spectra is found to occur earlier than in SN 1991T, suggesting SN 1999aa as a possible link between SN 1991T-like and Branch-normal supernovae. Comparing the observations with synthetic spectra, doubly ionized Fe, Si, and Ni are identified at early epochs. These are characteristic of SN 1991 T-like objects. Furthermore, in the day -11 spectrum, evidence is found for an absorption feature that could be identified as high velocity C II lambda 6580 or H alpha. At the same epoch C III lambda 4648.8 at photospheric velocity is probably responsible for the absorption feature at 4500 8. High-velocity Ca is found around maximum light together with Si II and Fe II confined in a narrow velocity window. Implied constraints on supernovae progenitor systems and explosion hydrodynamic models are briefly discussed.

  18. Spectropolarimetry of SN 2011fe

    NASA Astrophysics Data System (ADS)

    Milne, Peter; Williams, G.; Smith, P. S.; Smith, N.

    2014-01-01

    The Supernova Spectropolarimetry Project is a recently formed collaboration between observers and theorists that focuses on decoding the complex, time-dependent spectropolarimetric behavior of supernovae (SNe) of all types. Using the CCD Imaging/Spectropolarimeter (SPOL) at the 61" Kuiper, the 90" Bok, and the 6.5-m MMT telescopes, we obtain multi-epoch observations of each target, aiming to construct the most comprehensive survey to date of supernovae in polarized light. We present spectropolarimetry of SN 2011fe obtained for 8 epochs from August 2011-April 2012. The near-peak spectra show the evolution of the SiIIλ6355Å feature, as well as other polarized line features. The late nebular spectra show the line ratios and line profiles of the forbidden iron-peak elements. The spectral series permit estimation of the interstellar polarization. Collectively, these observations permit a study of the evolution of the emission from a NUV-blue type Ia supernova.

  19. The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode As Deflagrations?

    SciTech Connect

    Phillips, M.M.; Li, W.; Frieman, J.A.; Blinnikov, S.I.; DePoy, D.; Prieto, J.L.; Milne, P.; Contreras, C.; Folatelli, Gaston; Morrell, N.; Hamuy, M.; Suntzeff, N.B.; Roth, M.; Gonzalez, S.; Krzeminski, W.; Filippenko, A.V.; Freedman, W.L.; Chornock, R.; Jha, S.; Madore, B.F.; Persson, S.E.; /Las Campanas Observ. /UC, Berkeley, Astron. Dept. /Chicago U., Astron. Astrophys. Ctr. /KICP, Chicago /Fermilab /Moscow, ITEP /Garching, Max Planck Inst. /Ohio State U., Dept. Astron. /Arizona U., Astron. Dept. - Steward Observ. /Chile U., Santiago /Texas A-M /Carnegie Inst. Observ. /KIPAC, Menlo Park /Caltech, IPAC /Notre Dame U. /South African Astron. Observ. /Cape Town U. /Washington U., Seattle, Astron. Dept. /New Mexico State U. /Chicago U., FLASH /Baltimore, Space Telescope Sci.

    2006-11-14

    We present extensive u{prime}g{prime}r{prime}i{prime} BV RIY JHK{sub s} photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called 'the most peculiar known type Ia supernova'. Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal type Ia supernovae. Our Y JH photometry of SN 2005hk reveals the same peculiarity in the near-infrared. By combining our optical and near-infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from {approx} 10 days before to {approx}60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near-infrared wavelengths, are all in reasonable agreement with model calculations of a 3D deflagration which produces {approx} 0.25 M{sub {circle_dot}} of {sup 56}Ni.

  20. Calculation of the Transition from Pairing Vibrational to Pairing Rotational Regimes between Magic Nuclei {sup 100}Sn and {sup 132}Sn via Two-Nucleon Transfer Reactions

    SciTech Connect

    Potel, G.; Barranco, F.; Marini, F.; Idini, A.; Vigezzi, E.; Broglia, R. A.

    2011-08-26

    Absolute values of two-particle transfer cross sections along the Sn-isotopic chain are calculated. They agree with measurements within errors and without free parameters. Within this scenario, the predictions concerning the absolute value of the two-particle transfer cross sections associated with the excitation of the pairing vibrational spectrum expected around the recently discovered closed shell nucleus {sub 50}{sup 132}Sn{sub 82} and the very exotic nucleus {sub 50}{sup 100}Sn{sub 50} can be considered quantitative, opening new perspectives in the study of pairing in nuclei.

  1. SAINTS - The SN 1987A Intensive Study

    NASA Astrophysics Data System (ADS)

    Kirshner, Robert

    2010-09-01

    SAINTS is a program to observe SN 1987A, the brightest supernova since 1604, as it matures into the youngest supernova remnant at age 23. HST is the essential tool for observing SN 1987A's many physical components. A violent encounter is underway between the fastest-moving debris and the circumstellar ring: shocks excite "hotspots." Radio, optical, infrared and X-ray fluxes have been rising rapidly: we have organized VLT, Spitzer, and Chandra observations to understand the several emission mechanisms at work. The inner debris, excited by radioactive isotopes from the explosion, is now resolved and seen to be aspherical, providing direct evidence on the shape of the explosion itself and on dust that formed in the debris. Questions about SN 1987A remain unanswered. For example, whereis the compact object whose formation sent neutrinos our way in February 1987 ? A rich and unbroken data set from SAINTS will help answer these central questions and will build an archive for the future to help answer questions we have not yet thought to ask. For Cycle 18, these data will include novel observations with the IR channel of WFC3 and UV observations with COS.

  2. Preparation and Characterization of SnO2/Ag Hollow Microsphere via a Convenient Hydrothermal Route.

    PubMed

    Qiao, Xiuqing; Hu, Fuchao; Hou, Dongfang; Li, Dongsheng

    2016-04-01

    SnO2/Ag hollow microsphere, assembled form SnO2 and Ag nanoparticles, was synthesized via a facile one-step hydrothermal synthesis method using Na2SnO3.3H2O, CO(NH2)2 and AgNO3 as raw materials. XRD, SEM, and TEM results revealed that the obtained SnO2/Ag hollow microsphere with diameters of ca.3-5 µm was built from uniformly distributed rutile SnO2 and cubic Ag nanoparticles. Moreover, XPS results indicate the existence of strong interaction between Ag and SnO2 nanoparticles, rather than simply physical contact, endowing the SnO2/Ag hollow microspheres with excellent photocatalytic performance in the degradation of RhB solution under visible light irradiation. PMID:27451773

  3. Developing a Clinically Useful Calcium Isotope Biomarker

    NASA Technical Reports Server (NTRS)

    Romaniello, Stephen J.; Anbar, Ariel D.; Gordon, Gwyneth W.; Skulan, Joseph L.; Smith, Scott M.; Zwart, Sara R.; Monge, Jorge; Fonseca, Rafael

    2016-01-01

    Naturally-occurring Ca is mixture of six isotopes Ca-40, Ca-42, Ca-43, Ca-44, Ca-46, Ca-48). Biological reaction rates and equilibrium constants depend slightly, but measurably, on atomic mass, causing the relative abundances of Ca isotopes to vary between different tissues. During bone formation, light isotopes of Ca are preferentially incorporated into bone, leaving soft tissue depleted in light isotopes. In contrast, bone resorption exhibits no isotopic preference, and thus transfers the light isotope signature of bone back to soft tissue. This balance makes the Ca isotope composition of soft tissue (e.g. serum, urine) a highly sensitive, quantitative tracer for whole-body bone mineral balance (BMB).

  4. Resolving the stellar sources of isotopically rare presolar silicate grains through Mg and Fe isotopic analyses

    SciTech Connect

    Nguyen, Ann N.; Messenger, Scott

    2014-04-01

    We conducted multi-element isotopic analyses of 11 presolar silicate grains from the Acfer 094 meteorite having unusual O isotopic compositions. Eight grains are {sup 18}O-rich, one is {sup 16}O-rich, and two are extremely {sup 17}O-rich. We constrained the grains' stellar sources by measuring their Si and Mg isotopic ratios, and also the {sup 54}Fe/{sup 56}Fe and {sup 57}Fe/{sup 56}Fe ratios for five grains. The Mg and Fe isotopic measurements were conducted after surrounding matrix grains were removed for more accurate ratios. Most of the {sup 18}O-rich silicates had anomalous Mg isotopic ratios, and their combined isotopic constraints are consistent with origins in low-mass Type II supernovae (SNe II) rather than high-metallicity stars. The isotopic ratios of the {sup 16}O-rich silicate are also consistent with an SN origin. Mixing small amounts of interior stellar material with the stellar envelope replicated all measured isotopic ratios except for {sup 29}Si/{sup 28}Si and {sup 54}Fe/{sup 56}Fe in some grains. The {sup 29}Si/{sup 28}Si ratios of all SN-derived grains are matched by doubling the {sup 29}Si yield in the Ne- and Si-burning zones. The {sup 54}Fe/{sup 56}Fe ratios of the grains imply elemental fractionation in the Si/S zone, or introduction of isotopically solar Fe by secondary processing. The two highly {sup 17}O-rich silicates exhibited significant {sup 25}Mg and/or {sup 26}Mg enrichments and their isotopic ratios are best explained by strong dilution of 1.15 M {sub ☉} CO nova matter. We estimate that ∼12% and 1% of presolar silicates have SN and nova origins, respectively, similar to presolar SiC and oxides. This implies that asymptotic giant branch stars are the dominant dust producers in the galaxy.

  5. The Untimely Demise of SN 2008S

    NASA Astrophysics Data System (ADS)

    Sugerman, Ben; Benge, Ashlee; Cosgrove, Andrew; Snyder, Kayla

    2016-01-01

    Supernova (SN) 2008S in the "Fireworks Galaxy" (NGC 6946) has been enigmatic ever since its initial outburst was discovered in Feb 1, 2008. Initially classified a Type IIn due to early spectral features, it's subsequent spectral and photometric behavior over the first ~200 days led to two divergent explanations for the event. Citing photometric behavior atypical for any known explosion mechanisms, some have concluded this was "supernova imposter," such as a giant eruption in a massive Luminous Blue Variable star. Others report that its evolution was in fact consistent with the faintest Type-IIP SNe, which combined with the discovery of an intermediate-mass progenitor in mid-IR imaging, led to the conclusion that it was an electron-capture SN. Using a combination of ground-based, Hubble Space Telescope optical and near-infrared, and Spitzer Space Telescope mid-infrared imaging, we have traced the optical-through-infrared evolution of the SN from outburst to disappearance by 2014. We show that the limited intermediate-time optical data are consistent with radioactive 56-Co decay, however there are not enough late-time observations to assert with confidence whether or not the light curve supports a supernova hypothesis. We also show that the mid-infrared source identified as the progenitor is still present after the disappearance of the SN, suggesting either that this source is unrelated to the progenitor, or that the progenitor has returned to its pre-outburst state.

  6. Early Spectroscopic Identification of SN 2008D

    NASA Astrophysics Data System (ADS)

    Malesani, D.; Fynbo, J. P. U.; Hjorth, J.; Leloudas, G.; Sollerman, J.; Stritzinger, M. D.; Vreeswijk, P. M.; Watson, D. J.; Gorosabel, J.; Michałowski, M. J.; Thöne, C. C.; Augusteijn, T.; Bersier, D.; Jakobsson, P.; Jaunsen, A. O.; Ledoux, C.; Levan, A. J.; Milvang-Jensen, B.; Rol, E.; Tanvir, N. R.; Wiersema, K.; Xu, D.; Albert, L.; Bayliss, M.; Gall, C.; Grove, L. F.; Koester, B. P.; Leitet, E.; Pursimo, T.; Skillen, I.

    2009-02-01

    SN 2008D was discovered while following up an unusually bright X-ray transient (XT) in the nearby spiral galaxy NGC 2770. We present early optical spectra (obtained 1.75 days after the XT) which allowed the first identification of the object as a supernova (SN) at redshift z = 0.007. These spectra were acquired during the initial declining phase of the light curve, likely produced in the stellar envelope cooling after shock breakout, and rarely observed. They exhibit a rather flat spectral energy distribution with broad undulations, and a strong, W-shaped feature with minima at 3980 and 4190 Å (rest frame). We also present extensive spectroscopy and photometry of the SN during the subsequent photospheric phase. Unlike SNe associated with gamma-ray bursts, SN 2008D displayed prominent He features and is therefore of Type Ib. Partly based on observations made with ESO telescopes at the La Silla Paranal Observatory under program 080.D-0526, with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, and with the United Kingdom Infrared Telescope, which is operated by the Joint Astronomy Centre on behalf of the Science and Technology Council of the UK.

  7. SN1987A's Twentieth Anniversary

    NASA Astrophysics Data System (ADS)

    2007-02-01

    Looking back at 20 Years of Observations of this Supernova with ESO telescopes The unique supernova SN 1987A has been a bonanza for astrophysicists. It provided several observational 'firsts,' like the detection of neutrinos from an exploding star, the observation of the progenitor star on archival photographic plates, the signatures of a non-spherical explosion, the direct observation of the radioactive elements produced during the blast, observation of the formation of dust in the supernova, as well as the detection of circumstellar and interstellar material. ESO PR Photo 08a/07 ESO PR Photo 08a/07 SN1987A in the Large Magellanic Cloud Today, it is exactly twenty years since the explosion of Supernova 1987A in the Large Magellanic Cloud was first observed, at a distance of 163,000 light-years. It was the first naked-eye supernova to be seen for 383 years. Few events in modern astronomy have met with such an enthusiastic response by the scientists and now, after 20 years, it continues to be an extremely exciting object that is further studied by astronomers around the world, in particular using ESO's telescopes. When the first signs of Supernova 1987A, the first supernova of the year 1987, were noticed early on 24 February of that year, it was clear that this would be an unusual event. It was discovered by naked-eye and on a panoramic photographic plate taken with a 10-inch astrograph on Las Campanas in Chile by Oscar Duhalde and Ian Shelton, respectively. A few hours earlier, still on 23 February, two large underground detectors - in Japan and the USA - had registered the passage of high-energy neutrinos. Since SN 1987A exploded in the Large Magellanic Cloud (LMC), it was only accessible to telescopes in the Southern Hemisphere, more particularly in Australia, South Africa, and South America. In Chile, ESO's observatory at La Silla with its armada of telescopes with sizes between 0.5 and 3.6-m, played an important role. ESO PR Photo 08c/07 ESO PR Photo 08c/07 The

  8. Characteristics of Sn segregation in Ge/GeSn heterostructures

    NASA Astrophysics Data System (ADS)

    Li, H.; Chang, C.; Chen, T. P.; Cheng, H. H.; Shi, Z. W.; Chen, H.

    2014-10-01

    We report an investigation of Sn segregation in Ge/GeSn heterostructures occurred during the growth by molecular beam epitaxy. The measured Sn profile in the Ge layer shows that: (a) the Sn concentration decreases rapidly near the Ge/GeSn interface, and (b) when moving away from the interface, the Sn concentration reduced with a much slower rate. The 1/e decay lengths of the present system are much longer than those of the conventional group IV system of Ge segregation in the Si overlayer because of the smaller kinetic potential as modeled by a self-limited two-state exchange scheme. The demonstration of the Sn segregation shows the material characteristics of the heterostructure, which are needed for the investigation of its optical properties.

  9. Low-visibility light-intensity laser-triggered release of entrapped calcein from 1,2-bis (tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine liposomes is mediated through a type I photoactivation pathway

    PubMed Central

    Yavlovich, Amichai; Viard, Mathias; Gupta, Kshitij; Sine, Jessica; Vu, Mylinh; Blumenthal, Robert; Tata, Darrell B; Puri, Anu

    2013-01-01

    We recently reported on the physical characteristics of photo-triggerable liposomes containing dipalmitoylphosphatidylcholine (DPPC), and 1,2-bis (tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine (DC8,9PC) carrying a photo agent as their payload. When exposed to a low-intensity 514 nm wavelength (continuous-wave) laser light, these liposomes were observed to release entrapped calcein green (Cal-G; Ex/Em 490/517 nm) but not calcein blue (Cal-B; Ex/Em 360/460 nm). In this study, we have investigated the mechanism for the 514 nm laser-triggered release of the Cal-G payload using several scavengers that are known specifically to inhibit either type I or type II photoreaction pathways. Liposomes containing DPPC:DC8,9PC: distearoylphosphatidylethanolamine (DSPE)-polyethylene glycol (PEG)-2000 (86:10:04 mole ratio) were loaded either with fluorescent (calcein) or nonfluorescent (3H-inulin) aqueous markers. In addition, a non-photo-triggerable formulation (1-palmitoyl-2-oleoyl phosphatidylcholine [POPC]:DC8,9PC:DSPE-PEG2000) was also studied with the same payloads. The 514 nm wavelength laser exposure on photo-triggerable liposomes resulted in the release of Cal-G but not that of Cal-B or 3H-inulin, suggesting an involvement of a photoactivated state of Cal-G due to the 514 nm laser exposure. Upon 514 nm laser exposures, substantial hydrogen peroxide (H2O2, ≈100 μM) levels were detected from only the Cal-G loaded photo-triggerable liposomes but not from Cal-B-loaded liposomes (≤10 μM H2O2). The Cal-G release from photo-triggerable liposomes was found to be significantly inhibited by ascorbic acid (AA), resulting in a 70%–80% reduction in Cal-G release. The extent of AA-mediated inhibition of Cal-G release from the liposomes also correlated with the consumption of AA. No AA consumption was detected in the 514 nm laserexposed Cal B-loaded liposomes, thus confirming a role of photoactivation of Cal-G in liposome destabilization. Inclusion of 100 mM K3Fe(CN)6 (a

  10. Anomalous behavior of 2+ excitations around 132Sn

    NASA Astrophysics Data System (ADS)

    Terasaki, J.; Engel, J.; Nazarewicz, W.; Stoitsov, M.

    2002-11-01

    In certain neutron-rich Te isotopes, a decrease in the energy of the first excited 2+ state is accompanied by a decrease in the E2 strength to that state from the ground state, contradicting simple systematics and general intuition about quadrupole collectivity. We use a separable quadrupole-plus-pairing Hamiltonian and the quasiparticle random phase approximation to calculate energies, B(E2,0+-->2+) strengths, and g factors for the lowest 2+ states near 132Sn (Z>=50). We trace the anomalous behavior in the Te isotopes to a reduced neutron pairing above the N=82 magic gap.