On suprathermal corrections to reaction rates in astrophysical plasmas

Abstract

Reaction rates in astrophysical plasma can be affected by suprathermal particles naturally produced in the matter. The influence of this phenomenon on the relation between forward and reverse processes in extremely different astrophysical environments --the primordial and solar core plasmas-- is discussed. The suprathermal components of $ d + d \rightleftarrows n + {}^3\mathrm{He}$ , $ d + d \rightleftarrows p + t$ , $ n + {}^3\mathrm{He} \rightleftarrows p + t$ , $ n + {}^7\mathrm{Be} \rightleftarrows p + {}^7\mathrm{Li}$ , $ p + {}^7\mathrm{Li} \rightleftarrows \alpha + \alpha$ , $ n + {}^7\mathrm{Be} \rightleftarrows \alpha + \alpha$ , $ \alpha + {}^6\mathrm{He} \rightleftarrows n + {}^9\mathrm{Be}$ , and $ p + {}^{18}\mathrm{F} \rightleftarrows \alpha + {}^{15}\mathrm{O}$ reactions induced by MeV neutrons, protons, and $ \alpha$ -particles are calculated and their role is clarified. In the primordial plasma, the reverse rates are partly determined by the suprathermal reactions capable of maintaining the processes as the Universe cools. It the solar core plasma, the reverse process $ \alpha + {}^{15}\mathrm{O} \rightarrow p + {}^{18}\mathrm{F}$ is fully controlled by the suprathermal component, and its rate can become equal to the rate of the forward reaction in the outer core, that nullifies the straightforward nuclear flow between the CNO-I and CNO-III branches. This result together with previous findings on the suprathermal impact on running of the CNO-II branch may serve as an argument to incorporate suprathermal processes in nucleosynthesis calculations for stars fueled by the CNO cycle.