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  • 1
    Electronic Resource
    Electronic Resource
    Calculation of optical conductivity and electron energy loss spectra of YBa2Cu3O7 in the 10–160 eV range (1993)
    Springer
    The European physical journal 90 (1993), S. 283-288 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We calculate the high frequency macroscopic dielectric function ε(ω) of YBaCuO by treating the solid as a dense gas of polarizable cells. The cell polarizability is constructed from independent atomic contributions within a local-density based random phase approximation (LDRPA) and improvements thereof. In this way, interband transitions are treated very schematically but transitions from the core-like Ba 5p 6 shell are treated quite well. This is important, because the intense Ba 5p–5d like giant dipole resonance provides about half of the optical conductivity around 20 eV and contributes strongly to the all-valence electron plasma frequency. The calculated conductivity is in quite good agreement with experiment in magnitude and shape above 15–20 eV. The calculated EELS is similar in magnitude and shape to the experimental one but shifted to higher energies: in particular, the valence electron plasmon occurs around 33(26) eV in the calculated (experimental) EELS. This is reasonable, since the real solid involves lowlying charge transfer excitations and interband transitions which are absent in the atomic model of the YBaCuO unit cell. In the atomic model, the corresponding intensity is taken into account by higher frequency atomic transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01433049
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  • 2
    Electronic Resource
    Electronic Resource
    Oxygen diffusion and dynamical disorder in high-T c superconductors: low frequency noise in superconducting tunnel junctions (1993)
    Springer
    The European physical journal 91 (1993), S. 277-284 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The equilibrium diffusion fluctuations of oxygen concentration in HTSC are considered as a possible source of the low frequency current/voltage noise in tunnel junctions near the transition temperature in the frames of the model independent phenomenological approach. The general expression for the noise spectrum,S(ω), is obtained. It is shown that the noise is “diffusion-like”,S(ω)≃ω−2, and it is proportional to the square of the contact current/voltage. The noise magnitude is sharply peaked near the maximal critical temperature achievable for a given type of HTSC by an optimal oxygen doping. The noise cutoff frequency, below which it can be observed on the thermal background, has the activation like temperature dependence and is estimated to be ≃1s −1. The other possible consequences of the oxygen concentration fluctuations in HTSC are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01344056
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Multiphoton ionization of many-electron atoms (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 31 (1987), S. 833-840 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We review the main experimental results obtained in the multielectron multiphoton ionization of rare gases. Multiple ionization is interpretated as a sequential process. We study the influence of many-electron effects in multiphoton ionization within the framework of the random phase approximation. This is applied to a calculation of the two-photon ionization cross section of xenon. Finally, the role of screening effects in the multiphoton stripping of heavy atoms (Xe) is estimated.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560310511
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    Paper (German National Licenses)
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