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

Abstract

The dynamical cluster-decay model (DCM) of Gupta and Collaborators has been used to study the decay of various Pt-isotopes 176, 182, 188, 196Pt* formed in 64Ni+112, 118, 124Sn and 132Sn+64Ni reactions. The evaporation residue (ER) and fission cross-sections (σER and σfiss) are calculated in reference to available experimental data at near- and sub-barrier energies. The calculated σER 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 196Pt* becomes much smaller, compared to other 176, 182, 188Pt*isotopes, and more so at higher c.m. energies, possibly due to additional eight neutrons of the radioactive 132Sn nucleus. Another interesting result of the DCM calculation is that, similar to other well-known Ni-induced (58, 64Ni+58, 64Ni and 64Ni+100Mo) reactions, an inbuilt ‘barrier lowering’ effect is also shown operating for σER as well as σfiss at sub-barrier energies in these reactions. Furthermore, the calculated σfiss shows a significant contribution of quasi-fission (σqf) 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.Communicated by Professor S Bass.