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  • 1985-1989  (2)
  • 1975-1979  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 274 (1975), S. 215-222 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The accuracy of the semiclassical approximation for Coulomb matrix elements is discussed. The absolute values of the matrix elements are in general well approximated, but the agreement of the semiclassical phases with the exact ones is less satisfactory. Therefore, we present a modified semiclassical approximation which essentially improves the values of the phases. This modified semiclassical approximation is obtained by the introduction of a complex saddle point integration method. Since both the absolute values and the phases of the matrix elements are well reproduced by the modified semiclassical approximation, quantities depending on the phase can now also be calculated in the semiclassical manner.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The triton-proton angular correlation function has been measured for the58Ni(α, t p)58Ni reaction leading to the ground state of the target nucleus. The obtained experimental data have been interpreted in terms of the direct break-up (fragmentation) of the alpha particle on the target nucleus potential. It is shown that the main features of the measured double differential cross section are well predicted by the DWBA theory of the break-up. The dependence of the elastic and inclusive break-up cross sections upon the fragment-target interaction potentials is discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 278 (1976), S. 139-143 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is demonstrated that the Mott-Schwinger interaction must be taken into account when analyses of polarisation measurements in proton scattering at energies below the Coulomb barrier are to be performed with high accuracy. A treatment of the effect is worked out in perturbation theory, and the reliability of the method is demonstrated. It is shown how the resulting badly converging series for the “Mott-Schwinger amplitude” can conveniently be summed by means of Padé-approximation. Numerical results are presented for several representative cases.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 281 (1977), S. 391-394 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The modified semiclassical approximation of Coulomb matrix elements is extended to include effects of distorting nuclear potentials in the scattering wave functions. The applicability and efficiency of the proposed semiclassical method are discussed. The advantages of this approximation are shown for a typical heavy-ion transfer reaction.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 48 (1987), S. 231-254 
    ISSN: 1572-9613
    Keywords: Discrete dynamics ; circle maps ; noise ; mean first passage times ; metastability ; escape rates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The problem of escape from a domain of attraction is applied to the case of discrete dynamical systems possessing stable and unstable fixed points. In the presence of noise, the otherwise stable fixed point of a nonlinear map becomes metastable, due to noise-induced hopping events, which eventually pass the unstable fixed point. Exact integral equations for the moments of the first passage time variable are derived, as well as an upper bound for the first moment. In the limit of weak noise, the integral equation for the first moment, i.e., the mean first passage time (MFPT), is treated, both numerically and analytically. The exponential leading part of the MFPT is given by the ratio of the noise-induced invariant probability at the stable fixed point and unstable fixed point, respectively. The evaluation of the prefactor is more subtle: It is characterized by a jump at the exit boundaries, which is the result of a discontinuous boundary layer function obeying an inhomogeneous integral equation. The jump at the boundary is shown to be always less than one-half of the maximum value of the MFPT. On the basis of a clear-cut separation of time scales, the MFPT is related to the escape rate to leave the domain of attraction and other transport coefficients, such as the diffusion coefficient. Alternatively, the rate can also be obtained if one evaluates the current-carrying flux that results if particles are continuously injected into the domain of attraction and captured beyond the exit boundaries. The two methods are shown to yield identical results for the escape rate of the weak noise result for the MFPT, respectively. As a byproduct of this study, we obtain general analytic expressions for the invariant probability of noisy maps with a small amount of nonlinearity.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1434-6079
    Keywords: 34.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract For 3.6 MeV He impact theL I andL III subshell ionization probabilities of Pt have been measured. Due to relativistic effects in the electron wave functions, theL I subshell ionization probabilityI LI (b) is strongly enhanced at small impact parameters exceeding evenI LIII (b) in nice agreement with the SCA theory.
    Type of Medium: Electronic Resource
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