Abstract
In an effort to study the effect of the entrance channel mass asymmetry on the fusion process at near-barrier energies, we have measured the fusion cross section and its distribution according to the different evaporation residues for the $^{28}\mathrm{Si}$${+}^{142}$Ce, $^{32}\mathrm{S}$${+}^{138}$Ba, and $^{48}\mathrm{Ti}$${+}^{122}$Sn systems. All these systems lead to the same compound nucleus $^{170}\mathrm{Hf}$. The measurements were performed using a delayed x-ray technique. For the last two systems we have also measured the fission cross sections in the same bombarding energy range. This experimental information can be used to restrict the free parameters of the statistical model used to account for the relative yield. A constrained and realistic statistical decay model is useful in reducing the uncertainties in the determination of the spin distribution from measurements of gamma multiplicities for these systems. The excitation function for the fusion cross section can be described using a schematic coupled channels calculation with realistic coupling strengths. Our results show no umambiguous effect that can be associated with the entrance channel mass asymmetry.
Published Version
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