Cluster decay of hot56Ni*formed in the32S+24Mgreaction

Abstract

The decay of ${}^{56}{\mathrm{Ni}}^{*},$ formed in ${}^{32}\mathrm{S}{+}^{24}\mathrm{Mg}$ reaction at the incident energies ${E}_{\mathrm{c}.\mathrm{m}.}=51.6$ and 60.5 MeV (where c.m. is the center of mass), is calculated as a cluster decay process within the preformed cluster-decay model of Gupta et al. [Phys. Rev. C 65, 024601 (2002)] reformulated for hot compound systems. Interestingly enough, the cluster decay process is shown to contain the complete structure of both the measured fragment cross sections and total kinetic energies (TKEs). The observed deformed shapes of the exit channel fragments are simulated by introducing the neck-length parameter at the scission configuration, which nearly coincides with the ${}^{56}\mathrm{Ni}$ saddle configuration. This is the only parameter of the model, which, though, is also defined in terms of the binding energy of the hot compound system and the ground-state binding energies of the various emitted fragments. For the temperature effects included in shell corrections only, the normalized $\ensuremath{\alpha}$-nucleus s-wave cross sections calculated for nuclear shapes with outgoing fragments separated within nuclear proximity limit (here $\ensuremath{\sim}0.3\mathrm{fm})$ can be compared with the experimental data, and the TKEs are found to be in reasonably good agreement with experiments for the angular momentum effects added in the sticking limit for the moment of inertia. The incident energy effects are also shown in predicting different separation distances and angular momentum values for the best fit. Also, some light particle production (other than the evaporation residue, not treated here) is predicted at these energies and, interestingly, ${}^{4}\mathrm{He},$ which belongs to evaporation residue, is found missing as a dynamical cluster-decay fragment. Similar results are obtained for temperature effects included in all the terms of the potential energy. The non-$\ensuremath{\alpha}$ fragments are now equally important, and hence present a more realistic situation with respect to experiments.