Alpha decay of thermally excited nuclei

Abstract

One of the prominent decay modes of heavy nuclei which are produced in astrophysical environments at temperatures of the order of 109 K is the α (4He) decay. Thermally enhanced α decay rates are evaluated within the standard scheme of a tunneling decay where the α particle tunnels through the potential barrier formed by its interaction with the daughter nucleus. Following the observation that there exists several excited levels with the possibility of an α decay when the daughter nucleus is at a shell closure, we focus in particular on decays producing daughter nuclei with the neutron number, N = 126. Within a statistical approach we find that the half-lives, t 1/2(T), for temperatures ranging from T = 0 to 2.4 GK can decrease by 1–2 orders of magnitude with the exception of the decay of 212Po which decays to the doubly magic daughter 208Pb, where t 1/2(T) decreases by 5 orders of magnitude. The effect of these thermally enhanced α decays on the r-process nucleosynthesis can be significant in view of the mass build-up at the waiting point nuclei with closed neutron shells.