From fusion hindrance to oscillations

Dipartimento di Fisica e Astronomia, Università di Padova, and INFN, Sezione di Padova, I-35131 Padova, Italy

^a e-mail: giovanna.montagnoli@pd.infn.it

Published online: 29 January 2015

Abstract

This paper is devoted mainly to the fusion hindrance phenomenon, in its various aspects. Recent experimental results on medium-light systems where the fusion Q-value is positive are discussed. The application of the coupled-channels model using a shallow ion-ion potential is illustrated for ^32,36S + ⁴⁸Ca. The detailed influence of nuclear structure on the low-energy fusion cross sections is shown for the pair of systems ⁴⁸Ti + ⁵⁸Fe and ⁵⁸Ni + ⁵⁴Fe, where the low-lying quadrupole modes have a different degree of collectivity. The sub-barrier excitation function of ⁴⁸Ti + ⁵⁸Fe is much larger than for ⁵⁸Ni + ⁵⁴Fe. The lighter symmetric system ²⁸Si +²⁸Si has been the object of recent experimental investigations. Its fusion cross sections have been measured in a wide energy range down to ≤1µb. Above the barrier, we have a clear indication of oscillations in the excitation function, probably due to the penetration of successive centrifugal barriers, that are in rather good agreement with previous calculations. The CC model using the shallow M3Y+ repulsion potential is able to reproduce also the sub-barrier part of the excitation function of ²⁸Si +²⁸Si.