The decay of the compound nucleus 215Fr* formed in the 11B+204Pb and 18O+197Au reaction channels using the dynamical cluster-decay model

Abstract

The decay of 215Fr* nucleus, formed in 11B+204Pb and 18O+197Au reactions, is studied by using the dynamical cluster-decay model (DCM) with effects of deformations and orientations of nuclei included in it. The observed decay is mainly via fusion–fission, with data collected for both the fission excitation functions and fission fragment anisotropies. The chosen reaction channels have entrance channel mass asymmetries lying on either side of the Bussinaro–Gallone critical asymmetry parameter. In agreement with experimental data and conclusions based on the statistical code PACE2, for fission excitation functions, our DCM calculations with ℓmax value used in accordance with the sticking moment of inertia also show no contribution of the quasi-fission component in fission cross-sections for both the reaction channels, measured at incident center-of-mass energy spread on either side of the Coulomb barrier. Due to deformation and orientation of nuclei, the fission mass distribution is asymmetric, and nearly independent of the entrance channel. Interestingly, for a best fit to data on fission cross-sections, an in-built ‘barrier lowering’ seems operative at sub-barrier energies for both the reactions under study. Also, the fission fragment anisotropies, calculated on DCM for the first time, using non-sticking moment of inertia are found consistent with experimental data for both the reaction channels, confirming beyond doubt the entrance channel's independence of the decay of 215Fr*.