Systematics of the fusion cross-section in heavy ion reactions

Abstract

We study the energy dependence of the fusion cross-section with the goal of understanding the evolution of the underlying reaction mechanism as a function of input channel parameters and the causes of its (non-)disappearance. The heart of this work is a systematic and as wide as possible overview of measured cross-sections. Normalized by the reaction cross-section and plotted as a function of the available energy per nucleon corrected for the Coulomb barrier, fusion crosssection show a rather universal behavior leading to a disappearance of the fusion around 10A MeV, except in the case of very asymmetric systems for which incomplete fusion persists and tends towards a constant value that can be explained in the frame of a simple geometrical approach. These trends are confirmed by the semiclassical Landau-Vlasov transport calculations. In heavy ion collisions, one observes complete fusion (CF) and/or incomplete fusion (IF) mechanisms of the two partners in the most central reactions over an impact parameter range whose width depends strongly on the incident energy [1]. From the Coulomb barrier to 6-8A MeV, only CF occurs and it accounts for the largest part of the reaction cross section.