The decay of the ${}^{246}\mathrm{Bk}$${}^{*}$ nucleus, formed in entrance channel reactions ${}^{11}\mathrm{B}+{}^{235}\mathrm{U}$ and ${}^{14}\mathrm{N}+{}^{232}\mathrm{Th}$ at different incident energies, is studied by using the dynamical cluster-decay model (DCM) extended to include the deformations and orientations of nuclei. The main decay mode here is fission. The other (weaker) decay channels are the light particles evaporation ($A⩽4$) and intermediate mass fragments ($5⩽A⩽20$). All decay products are calculated as emissions of preformed clusters through the interaction barriers. The calculated fission cross sections ${\sigma }_{\mathrm{fiss}}$, taken as a sum of the energetically favored symmetric and near symmetric fragments ($A_{\mathrm{CN}}/2\pm 7$ and $A=106\text{−}110$ plus complementary fragments) show an excellent agreement with experimental data at all experimental incident c.m. energies for both reactions, except for the top three energies in the case of the ${}^{11}\mathrm{B}+{}^{235}\mathrm{U}$ reaction. The disagreement between the DCM calculations and data at higher incident c.m. energies for the ${}^{11}\mathrm{B}+{}^{235}\mathrm{U}$ entrance channel is associated with the presence of additional effects of noncompound, quasifission (qf) components, in contradiction with the measured anisotropy effects which indicate the other entrance channel ${}^{14}\mathrm{N}+{}^{232}\mathrm{Th}$ to contain the noncompound nucleus contribution. The prediction of two fission windows, the symmetric fission (SF) and near symmetric or heavy mass fragments (HMFs), suggests the presence of a fine structure of fission fragments, which also need an experimental verification. The only parameter of the model is the neck length parameter $▵R$ whose value is shown to depend strongly on limiting angular momentum, which in turn depends on the use of sticking or nonsticking moment of inertia for angular momentum effects.

• Received 24 March 2008

DOI:https://doi.org/10.1103/PhysRevC.77.054613