Fusion excitation functions of 64Ni+112-132Sn reactions studied on the dynamical cluster-decay model

The dynamical cluster-decay model (DCM) of Gupta and Collaborators has been used to study the decay of various Pt-isotopes Pt-176,Pt-182,Pt-188,Pt-196* formed in Ni-64+Sn-112,Sn-118,Sn-124 and Sn-132+Ni-64 reactions. The evaporation residue (ER) and fission cross-sections (sigma(ER) and sigma(fiss)) are calculated in reference to available experimental data at near- and sub-barrier energies. The calculated sigma(ER) show excellent agreement with experimental data at all incident center-of-mass (c.m.) energies, with the characteristics of emitted light particles (LPs) showing a change with the increase of the iso-spin N/Z ratio of compound nucleus (CN). The only parameter of DCM, the neck-length parameter, for Pt-196* becomes much smaller, compared to other Pt-176,Pt-182,Pt-188*isotopes, and more so at higher c. m. energies, possibly due to additional eight neutrons of the radioactive Sn-132 nucleus. Another interesting result of the DCM calculation is that, similar to other well-known Ni-induced (Ni-58,Ni-64+Ni-58,Ni-64 and Ni-64+Mo-100) reactions, an inbuilt 'barrier lowering' effect is also shown operating for sigma(ER) as well as sigma(fiss) at sub-barrier energies in these reactions. Furthermore, the calculated sigma(fiss) shows a significant contribution of quasifission (sigma(qf)) at the highest one or two energies, and, due to the deformation and orientation effects of fission fragments, shows a change of the mass distributions from a predominantly symmetric to a predominantly asymmetric one with the increase in the N/Z ratio of CN. This change in fission mass distributions provides the possibility of fine-/sub-structure in fission products of Pt* isotopes.