Influence of rotation-induced nuclear deformation on alpha -particle evaporation spectra.

Abstract

The shapes of \ensuremath{\alpha}-particle spectra from hot, high-spin compound nuclei produced in energetic heavy-ion fusion reactions are analyzed within the framework of a statistical model. Contrary to claims made in the literature, good agreement is obtained between calculated and experimental spectra when the evaporation barrier of each nuclide in the complex cascade is assumed equal to its respective absorption channel barrier. The dependence of the shape of \ensuremath{\alpha}-particle spectra on nuclear deformation is discussed both in terms of the transmission coefficients and the spin-dependent level density of deformed nuclei. For deformations of the magnitude given by the rotating liquid drop model, \ensuremath{\alpha}-particle spectra and effective barriers are insensitive to whether deformed or spherical nucleus transmission coefficients are used. It is important, however, to include the deformation dependence in the nuclear level density. Model calculations indicate that the shape of \ensuremath{\alpha}-particle spectra may be quite insensitive to large deformations.