Electron Capture Reactions and Beta Decays in Steller Environments

Abstract

Electron capture reactions on Ni and Co isotopes are investigated by shell model calculations in steller environments. The capture rates depend sensitively on the distribution of the Gamow‐Teller (GT) strength. The capture rates obtained by using GXPF1J Hamiltonian for fp‐shell are found to be consistent with the rates obtained from experimental GT strength in 58Ni and 60Ni. Capture rates in Co isotopes, where there were large discrepancies among previous calculations, are also investigated. Beta decays of the N = 126 isotones are studied by shell model calculations taking into account both the GT and first‐forbidden (FF) transitions. The FF transitions are found to be important to reduce the half‐lives by twice to several times of those by the GT contributions only. Implications of the short half‐lives of the waiting point nuclei on the r‐process nucleosynthesis are discussed for various astrophysical conditions.