Proton and neutron exchange as a prelude to fusion at near-barrier energies

TL;DR

This paper investigates how neutron and proton exchange influence fusion reactions near the Coulomb barrier, highlighting differences between open-shell and closed-shell nuclei through experimental data and theoretical calculations.

Contribution

It provides new insights into the role of nucleon exchange and shell effects on fusion cross-sections near the barrier, with comparisons between different isotopic systems.

Findings

Open-shell nuclei show higher fusion cross-sections than closed-shell counterparts.

Coupled channels calculations fit closed-shell data but underpredict open-shell fusion.

Shell effects and multi-nucleon exchange significantly influence fusion behavior.

Abstract

Systematic examination of fusion for $^{39,41,45,47}$K + $^{28}$Si and $^{36,44}$Ar + $^{28}$Si provides insight into the impact of neutron and proton exchange on fusion for nuclei at and near the N=20 and N=28 shells. Comparison of the reduced excitation functions reveals a marked difference between the behavior of open-shell and closed-shell systems. While coupled channels calculations provide a good description for the closed-shell nuclei they significantly under-predict the fusion cross-section for open-shell nuclei. The observed trends are examined in the context of a potential energy surface, including shell effects, and multi-nucleon exchange with consideration of Pauli-blocking.