Sub-barrier fusion of two nuclei

TLDR

Anomalous sub‑barrier fusion of massive nuclei was discovered in 1980. The study investigates the couplings and underlying dynamics of sub‑barrier fusion, focusing on quasi‑elastic channels such as inelastic scattering and nucleon transfer. Coupling of intrinsic degrees of freedom to tunnelling enhances barrier penetration, as illustrated by models developed between 1983 and 1985. Experimental cross sections for sub‑barrier fusion exceed simple tunnelling predictions and depend strongly on the valence structure, with recent studies of quasi‑elastic scattering and partial‑wave distributions supporting this.

Abstract

In 1980 the anomalous sub-barrier fusion of two massive atomic nuclei was discovered. The author examines the experimental findings that the cross sections for sub-barrier fusion far exceed simple quantum tunnelling expectations, and the magnitude of the excess fusion is particularly sensitive to the valence structure of the collision partners. The phenomenon is interpreted as one which occurs when intrinsic degrees of freedom of the dinuclear system couple to the tunnelling degree of freedom. Several models, developed during the period from 1983-5, serve to illustrate the salient features of coupling-aided barrier penetration. The author discusses the nature of the couplings and the underlying dynamics, focusing attention on the quasi-elastic channels (inelastic scattering and nucleon transfer). Results of studies on quasi-elastic scattering and of the fusion partial-wave distributions, completed during the past three years, are then presented.