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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: On Fe films evaporated on pyrolytic graphite, thick C layers segregate during high-temperature (above about 800 K) light ion irradiation if the penetrating ions are energetic enough to reach the Fe-graphite interface. The thickness of the C segregated layer and the C depth distribution in the Fe film have been determined with 2-MeV 4He+ Rutherford backscattering. A steady-state carbon overlayer is reached at high fluences (above about 1019 particles/cm2), the thickness of which depends on the energy of the irradiating beam for a given thickness of the Fe evaporated film. The anisotropic structure of the pyrolytic graphite substrate influences the thickness of the steady-state C overlayer, thicker C layers being measured for edge-oriented C substrates. Using the Monte Carlo code trim, the production of defects in the graphite substrate has been calculated for different thicknesses of the C overlayer. The total amount of defects produced in the graphite substrate has been identified as the parameter regulating the growth and the steady-state value of the C overlayer. With the depth distributions of defect production generated by trim as source functions, the diffusion of C interstitials in graphite under the influence of recombination with vacancies has been modeled. The segregating C fluxes are identified with the fluxes of interstitials arriving at the Fe/graphite substrate interface for a suitable choice of the parameters in the diffusion equation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 1893-1897 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Depth profiles of 10-keV deuterium implanted in nickel were obtained during implantation through elastic recoil detection between 233 and 313 K. The profiles were allowed to reach saturation at each measured temperature. At the lowest temperature, measurements with various implantation fluxes were performed. Aside from surface peaks, the depth profiles show a uniform density of deuterium in the implanted layer and the shape of these profiles is independent of the sample temperature or implantation fluence or flux. The temperature and fluence dependence could be successfully reproduced with a trapping-detrapping model considering three different trap binding energies. Two of the model parameters are in good agreement with previous calculations performed to reproduce reemission measurements.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Hyperfine interactions 38 (1987), S. 741-759 
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Collinear Laser Ion Beam Spectroscopy (CLIBS) investigates hyperfine structures (hfs) and isotope shifts (IS) in spectral lines and is well suited for the study of nuclear moments of short-lived isotopes. It is fast, highly selective, highly sensitive and allows many experimental alternatives. The high accuracy makes it also an interesting tool for atomic physics. A basic experimental setup is described. Results for nuclear moments and radii in Sm, Eu, Gd show that the accuracy of hfs and IS data is much better than the resulting moments. We discuss the hfs-anomaly and its dependence on atomic quantum numbers (L, S, J) and show that its determination is possible without the knowledge of the nuclear magnetic moments. A hfs-anomaly in respect of the nuclear quadrupole moment was not found. IS-measurements are used to determine permanent and fluctuating nuclear deformation. The standard interpretation is inconsistent in the case of Eu. Modifications of the theory are suggested. Crossed second order (CSO) effects affect the IS values. We show that CSO-effects may help to determine the field effect of the IS experimentally.
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  • 4
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mossbauer spectra of a vacuum deposited 95 nm thick57Fe film sandwiched between 35 nm copper layers on a beryllium substrate were measured during and after implantation with 60 keV D3 + ions to a fluence of 1.2×1018 D+/cm2. The modifications of the spectra indicate that at the target temperature of 100 K deuterium is mainly trapped at defects in the α-iron lattice or reemitted. Hydride formation is observed only weakly when the fluence exceeds 1018 D+/cm2. After annealing at room temperature, a complete recovery of the ordinary α-iron spectrum is observed.
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  • 5
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mit Hilfe des Mikro-Thermoanalysators und des Wärmeflußcalorimeters DSC 111 der Fa. Setaram wurden die Entropien für den Phasenübergang Chalcopyrit-Zinkblende von AIBIIIC 2 VI - und AIIBIVC 2 V -Verbindungen bestimmt. Aus diesen Experimenten kann nicht geschlossen werden, welche Ordnung der Übergang besitzt. In der Diskussion wird jedoch gezeigt, daß ein Übergang erster Ordnung wahrscheinlich ist. Eine einfache Korrelation zwischen dem Gitterkonstantenverhältnis, extrapoliert bis zum Schmelzpunkt und der auf den Schmelzpunkt reduzierten Umwandlungstemperatur gestattet die Vorhersage von Phasenumwandlungen.
    Abstract: Резюме С помощью микротермо анализатора Сетарам и ДСК 111с тепловым потоком было определено изме нение энтропии при фа зовом переходе типа халько пирит-сфалерит для соединений АIBIIIC 2 VI и АIBIVC 2 V . На основе полученных результа тов не представилось возможным установит ь порядок перехода, но в обсуждении указывае тся как на переход первого порядка. На ос нове простой корреля ции между отношением постоянн ых решетки, экстраполированных до температуры плавл ения, и приведенной темпера турой фазового перехода, можно устан овить степень разупо рядочения.
    Notes: Abstract The entropy change of the phase transition from the chalcopyrite to the sphalerite structure of compounds AIBIIIC 2 VI and AIIBIVC 2 V was determined with a Setaram Microthermalanalyzer and a DSC 111 heat flow calorimeter. From these results one can not generally decide the order of the phenomenon, but the discussion gives hints as to a first-order transition. On the basis of a simple correlation between the ratio of the lattice constants extrapolated up to the melting temperature and the reduced temperature of the phase transition, it is possible to predict the order disorder behaviour.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4860-4866 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new theoretical framework has been developed which is applicable to the implantation and ion-induced release of hydrogen isotopes in graphite. It provides a physical basis and a refinement of the predictions of the simple model of local saturation and mixing. The model treats the trapping at defects and a local release of trapped atoms by nuclear knock-on. Ion deposition and damage functions are taken from trim simulations. The detrapped atoms may become retrapped or recombine to molecules, which then are transported to the surface by fast molecular diffusion, and subsequently released. By the choice of suitable rate constants in the model calculations, different experimental findings for the implantation and high-fluence self-reemission of deuterons in graphite may be explained consistently. Examples cover the saturation as a function of temperature and energy, depth profiles, gas reemission, thermal desorption, and effects of predamage.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 2733-2738 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The permeation of 2–22-keV deuterons implanted into 25-μm-thick cold-rolled Ni foils was studied near room temperature. The results are generally characterized by a time lag τ and a steady-state permeation rate J. The variation of τ with beam intensity and temperature indicates an average relative concentration of ∼4×10−4 of saturable bulk traps of binding energy 0.26±0.01 eV, plus a larger concentration of weaker traps. At the highest energy, J is well described by theory.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 2225-2226 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Characteristic spectra of light emission from CH molecules and hydrogen atoms sputtered from hydrogen-implanted graphite are observed. The relative intensities from both species vary with the implanted fluence. The CH yield remains constant while the Hα yield increases. This is consistent with two binding states of implanted hydrogen in graphite.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3833-3837 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Soft carbonized layers prepared in a glow discharge, with a hydrogen concentration of H:C∼4/3, are exposed to helium ion bombardment at energies between 0.3 and 2.6 MeV. A strong ion-induced depletion of up to 3×103 H atoms per incident 4He+ ion is observed by means of high-energy ion beam analysis. The hydrogen release is shown to be a local process, with the electronic energy deposition as the main responsible mechanism. The results are successfully compared to a model which takes into account local bond breaking and retrapping and the local formation of hydrogen molecules.
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  • 10
    Publication Date: 2011-08-19
    Description: The basic models that have been used over the last 15 years to describe the accumulation and release of solar wind-related species at lunar conditions at the lunar surface are reviewed. Recent results which show that these models are not totally valid are discussed. It is suggested that mature lunar surface soils may act as efficient converters for transforming the flux of energetic solar wind protons into a flux of low-energy hydrogen and water molecules continuously injected into the lunar atmosphere.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
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