Fission following fusion of Ni+Sn.

Abstract

Excitation functions for fission were measured for $^{58,64}\mathrm{Ni}$ beams incident on the even $^{112\ensuremath{-}124}\mathrm{Sn}$ targets at energies extending from well below to about 1.5 times the Coulomb barrier. Fission was identified by kinematic coincidence between fission fragments. Angle integrated fission cross sections were obtained from angular distributions taken at several energies for all systems. From these and the previously measured cross sections for evaporation residues, we obtain the total fusion cross sections and fission probabilities over the energy range $150\ensuremath{\lesssim}{E}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\lesssim}240$ MeV. The competition between particle evaporation and fission in the compound nuclei is compared to statistical model calculations. A good description of the data for all 14 systems is achieved with the use of a single set of parameters. The model includes fission barriers with finite range and nuclear diffuseness effects, and partial-wave distributions for fusion that are qualitatively consistent with those from microscopic reaction model calculations. The fusion excitation functions are analyzed in terms of the dynamical fusion model of Swiatecki et al. Within this model we extract new values for the "extra-push" parameters.