Thermal effects on long-lived α decays in astrophysical nucleosynthesis

Alpha decay is an important competing process in astrophysical nucleosynthesis. In this work, thermal effects on several long-lived α decays relevant to the s -, r -, and p -processes are investigated within a microscopic coupled-channels framework combined with an effective- Q α approach. The α -daughter interaction is described by a temperature-dependent double-folding potential based on the density-dependent Migdal interaction, and the thermal contribution of nuclear excitations is evaluated by including both experimentally known discrete levels and the continuum part of the level density. Calculations for twelve selected long-lived α -emitters show that the direct thermal modification of the α -daughter potential is negligible at typical stellar temperatures, whereas the dominant thermal effect arises from the increase in the effective decay energy associated with the thermal population of parent states. The magnitude of the enhancement is found to depend on both the low-lying level structure of the parent nucleus and the ground-state decay energy. In contrast to the very large enhancements suggested in the early pioneering work of Perrone and Clayton [ Astrophys. Space~Sci. 11, 451 (1971) ], the present results indicate a more moderate thermal enhancement for the nuclei considered here. For most cases, the half-life reduction remains limited in the astrophysically relevant temperature range, although several low- Q α nuclei exhibit stronger enhancements toward the higher temperatures. These results provide updated estimates of thermal modifications to long-lived α -decay half-lives under astrophysical conditions, which may be useful for future studies in nuclear astrophysics.