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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 30 (1983), S. 117-122 
    ISSN: 1432-0630
    Keywords: 61.70 ; 72.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Fluctuations in the number of vacancies in metals in thermal equilibrium lead to resistivity fluctuations. Analysis of these fluctuations permits measurement of both formation and migration enthalpy of the vacancies. The power spectrum of the fluctuations is calculated using a series of statistically independent pulses. It can be derived from the diffusion equation for any geometry of the vacancy sinks. Vacancy diffusion to the surface of a thin plate or of a sphere are treated as examples. The measurability of vacancy noise is assessed. It should also be possible to measure vacancy noise during irradiation. It is predicted that correlated vacancy creation, which may occur during irradiation, will cause an increase in the power spectrum.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 22 (1980), S. 185-187 
    ISSN: 1432-0630
    Keywords: 06 ; 07 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract New methods for thermal-equilibrium investigations of atomic vacancies or of dislocation movements in metals require measurements of minute resistance fluctuations. The accuracy of such measurements is limited by thermal noise from the resistor. The present paper proposes a method for analysing resistance fluctuations independent of voltage noise.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0630
    Keywords: 06 ; 07 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A novel method is presented for measuring the spectral density of resistance fluctuations without the explicit determination of the voltage background noise (Johnson noise, pre-amplifier noise). The output of a standard ac bridge excited by a single-frequency alternating current is demodulated by two phase-sensitive detectors which operate in quadrature. When the phase difference between excitation and detection is properly set, the real part of the cross-spectral density of the two demodulators shows only the spectral density of the resistance fluctuations and not the disturbing background noise. The feasibility of our new method is demonstrated by measurements of 1/f noise of a thin-film A1 sample.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0630
    Keywords: 61.70 ; 81
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By means of an integrated source-specimen technique the temperature dependence of positron lifetimes and annihilation lineshapes has been measured, on the same specimens of gold and cadmium from 4.2K to the melting points, and also in electronirradiated and quenched gold. The anomalous temperature dependence of positron annihilation at intermediate temperatures (200 to 350 K in Cd, 270 to 750 K in Au) discovered by Lichtenberger, Schulte, and MacKenzie is confirmed. The data are incompatible with the idea that the intermediate temperature dependence is due to thermal expansion. They are well explained by an extension of the trapping model which includes the formation of metastable self-trapped positrons. From lineshape measurements after electron irradiation at 180 K and after quenching it is deduced that the trapping rate of positrons at vacancy-type defects in Au is temperature independent below room temperature.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 07.77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A slow-positron source has been installed in the therminal of an electrostatic 6.5 MeV accelerator and provides a monoenergetic positron beam in the few-MeV range. It will be used to operate a “fast” positron lifetime spectrometer based onβ + γ coincidences. The properties of the beam, the expected performance of the spectrometer, its advantages over conventionalγγ lifetime measurements, a number of intended applications, as well as recent positron-electron scattering experiments and plans for positron channelling and channelling-radiation studies are outlined.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 15 (1990), S. 79-86 
    ISSN: 1434-6079
    Keywords: 31.20 ; 36.40 ; 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The alternating process of adsorption of Ag+ and trapping of a photoelectron on a (100) AgBr surface is investigated by quantum chemical calculations. The results give some insight into the initial steps of the photographic process (absorption of two photons which lead to the formation of a sublatent image).
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 6 (1987), S. 193-198 
    ISSN: 1434-6079
    Keywords: 31.15 ; 36.40 ; 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Having studied free silver clusters by quantum chemical calculations we now present a method to take into account the influence of a silver halide surface on adsorbed silver clusters. The model for the surface will be a silver halide cluster as frozen crystal section. The interactions are discussed in detail; a new bromide pseudopotential may be of special interest. Results with this method will be given in subsequent papers.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 6 (1987), S. 287-292 
    ISSN: 1434-6079
    Keywords: 31.20 ; 36.40 ; 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The adsorption of Ag+ and Ag on a (100) AgBr surface is investigated. Interstitial subsurface sites and incomplete surfaces (with ledges and kinks) are also considered. Equilibrium geometries, adsorption energies and ionization potentials have been calculated. Migration of neutral Ag on the surface and crystal growth of AgBr are discussed, and a comparison with other theoretical results is given.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 67 (1998), S. 157-173 
    ISSN: 0020-7608
    Keywords: electron correlations ; charge fluctuations ; correlation strength ; chemical bonds ; first-row homonuclear diatomic molecules ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We investigate, by means of ab initio calculations, the strength of electron correlations within covalent bonds: the first-row homonuclear diatomics serve as test cases. As an appropriate measure of the correlation strength, we introduce the reduction of the mean-square deviations of the electronic charges in localized orbitals forming a bond. A recently developed population analysis in terms of local operators derived from localized molecular orbitals is thereby used. The correlation-strength parameter depends only weakly on dynamical correlations as test calculations demonstrate. Therefore, the full-valence complete active space self-consistent field (CASSCF) approximation is applied in order to study the changes in the correlation strength with changing bond length for different types of bonds. A number of simple rules emerge from this discussion. In addition, we show that charge fluctuations are not only a reliable measure of intrabond correlation effects, but also can be used to monitor intraatomic quasi-degeneracy effects as well as the interdependence within multiple bonds.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 157-173, 1998
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 559 (1988), S. 17-26 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Oxoaluminate KLi4[AlO4]Transparent and colourless single crystals of Kli4[AlO4] have been prepared for the first time by heating mixtures of Li5AlO4 and K2O in the ratio 1:5 [Ni-tube, 950°C, 50 d]. The structure determination [four-circle diffractometer, MoKα, 1699 of 2427 I0 (hkl), R = 7.41%, Rw = 4.3%] proves the monoclinic space group P21/c with a = 554.4(3), b = 1544.1(7), c = 1103.3(6) pm, β = 109.71(5)°, parameters see text. Characterizing are “isolated” AlO4 groups with symmetry nearly Td. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, have been calculated.
    Notes: Erstmals wurde KLi4[AlO4] durch Erhitzen innig verriebener Gemenge von Li5AlO4 und K2O im molaren Verhältnis 1:5 [Ni-Bömbchen, 950°C, 50 d] dargestellt. Wir erhielten farblose monokline Einkristalle (P21/c) mit a = 554,4(3), b = 1544,1(7), c = 1103,3(6) pm, β = 109,71(5)°.Die Struktur wurde mittels Vierkreisdiffraktometerdaten [MoKα, 1699 von 2427 I0(hkl), R = 7,41%, Rw = 4,3%] bestimmt, Parameter siehe Text. Charakteristisch sind “isolierte” AlO4-Gruppen, Symmetrie nahezu Td. Der Madelunganteil der Gitterenergie, MAPLE, und Effektive Koordinationszahlen, ECoN, diese über Mittlere Fiktive Ionenradien, MEFIR, wurden berechnet.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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