Deformation and orientation effects in the decay of268Sg*formed in a30Si-induced reaction across the Coulomb barrier

Abstract

The dynamical cluster decay model (DCM) is used to study the decay of the ${}^{268}$Sg${}^{*}$ compound nucleus formed in the ${}^{30}$Si+${}^{238}$U reaction at above and below the Coulomb barrier energies. The neutron evaporation residues and fission cross sections are calculated in reference to the available data, including ${\ensuremath{\beta}}_{2i}$-static deformations with `optimum' orientations. The role of spherical and the ${\ensuremath{\beta}}_{2i}$-dynamic deformed choices of fragmentation are also studied explicitly at the highest 169 MeV energy. The fission fragment distribution is symmetric at above-barrier energies, where equatorial collisions are preferred, but becomes asymmetric when the nuclei approach in pole-to-pole configuration at sub-barrier energies. Therefore, at above-barrier energies the calculations are carried out by considering `hot fusion', equatorial collisions, whereas at sub-barrier energies the `cold fusion', polar configuration is considered. The asymmetric peaks at sub-barrier energies may be associated with some competing process, like quasifission. The analysis of polar and equatorial configurations suggests that larger barrier modification is required at sub-barrier energies for neutron evaporation residue and fission fragments, i.e., the contribution of barrier modification at sub-barrier energies is relatively higher for a cold elongated polar configuration as compared to a hot compact equatorial configuration. Finally, the potential energies surfaces for the Si-induced reaction are compared with the $S$-induced reaction on the ${}^{238}$U target, at comparable center of mass energies.