Why the complete fusion of weakly bound nuclei is enhanced at sub-barrier energies and suppressed above the barrier?

Abstract

In this paper we explain the reasons for the systematic behaviour of enhancement of the complete fusion cross section of weakly bound systems at sub-barrier energies and its suppression above the barrier, when compared with predictions from calculations which do not take into account breakup and transfer channels. The methodology used is the study of dynamic polarization potentials. At above barrier energies the net polarization potential due to direct breakup is dominant and repulsive, consequently fusion is suppressed. At sub-barrier energies, the enhancement of fusion cross section is consistent with recent experimental observations that nucleon transfer leading to breakup is dominant compared to direct breakup and produces attractive polarization potential.