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  • 1985-1989  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 323 (1986), S. 387-390 
    ISSN: 1434-601X
    Schlagwort(e): 21.65 ; 25.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Ample production of fast particles has been observed in intermediate heavy ion reactions [1]. These particles have often been related to sources having velocities close to half that of the beam and temperatures ranging between a few and several tens MeV. For such temperatures neither the low temperature Fermi gas model nor the Boltzmann gas model are valid. A more correct treatment is necessary in order to understand the relationship between the incident energy per nucleon, the excitation energy of the source and its temperature. In this short paper we give simple closed expressions allowing to interpolate between the Fermi and the Boltzmann regimes. In the following we consider a gas of fermions (Nucleons) at a temperatureT trapped in a square potential well of depthU. We shall not deal with the dynamics of the expansion of the gas except through the calculation of the particle evaporation rate. Likewise we do not consider the implications of a possible liquid gas transition [2]. We first approximate the variation of the chemical potential as a function of the temperature. Using that, we are able to compute and find approximations to the variations of the excitation energy with temperature and vice-versa. Finally we give expressions for the particle evaporation rate of a hot Fermi gas and compare them to the Weisskopf formula.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1434-601X
    Schlagwort(e): 25.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The angular and velocity distributions of incomplete fusion residues have been measured, around 30 AMeV projectile incident energy, for a number of systems with varying mass asymmetries, from the most asymmetric S+Cu, to the almost symmetric Ar+Ca. The main experimental finding is that the parallel width of the velocity distribution increases sharply for decreasing asymmetries, while the perpendicular width remains nearly constant. Using, as data, the widths and mean values of the velocity distributions, it was possible to derive the number of preequilibrium particles emitted by the projectile and by the target. It was found that target emission becomes noticeable only when the center of mass velocity of the target, at nuclear contact, exceeds approximately 2.5 cm/ns. This underlines the relevance of the center of mass velocities in the preequilibrium emission and incomplete fusion processes.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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