Roles of survival probability and barrier reduction in heavy ion fusion induced by break up

Abstract

Incorporating the mathematical procedure developed by Farina within the framework of our effective fusion barrier model, expressions are given for the intensity of transmitted wave both below and above the barrier for the estimate of nucleus-nucleus fusion cross section (σ F ). When one of the colliding nuclei is a neutron rich weakly bound light nucleus we obtain an expression for the survival probability of such participant using time scales involved in fusion formation as well as neutron emission processes and incorporate this in the σ F formula. In effect, this modification leads to reduced σ F as compared with the fusion of corresponding stable nuclei. Applying this procedure very good fits to the σ F data are obtained for the systems 9 Be + 29 Si and 9 Be+ 12 C, using neutron separation energy n = 1.67 MeV for 9 Be. We introduce additional modification in the effective fusion barrier model to incorporate the feature of reduction of barrier height due to very small n (<1 MeV). It is found that in such case, the net effect of break up process generating the reductions of survival probability and barrier height leads to the over all enhancement of σ F . Taking into account the fact that for 11 Li two-neutron separation energy is 0.2 MeV, we explicitly calculate σ F for the system 11 Li+ 150 Sm which is to be confirmed experimentally. PACS: 25.70.-Z; 25.70.Jj