Alpha decay of thermally excited nuclei

One of the prominent decay modes of heavy nuclei which are produced in astrophysical environments at temperatures of the order of 10(9) K is the alpha (He-4) decay. Thermally enhanced alpha decay rates are evaluated within the standard scheme of a tunneling decay where the alpha 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 alpha 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 Po-212 which decays to the doubly magic daughter Pb-208, where t (1/2)(T) decreases by 5 orders of magnitude. The effect of these thermally enhanced alpha 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.