Abstract
Using the shell-model Lanczos method, we calculate the Gamow-Teller matrix elements for beta transitions of astrophysical interest from excited states of ,141 keV; ,181 keV) to the ground and excited states of . The level schemes of low-lying positive-parity states in these nuclei and in the analogous isotonic nuclei Mo are reproduced fairly well within a model space consisting of low-seniority excitations in the 1g2d shell, which are mixed via the Kallio-Kolltveit effective interaction. The calculations lead to a half-life of ∼20 yr at a stellar temperature of 3× K typical for the s process with a ,nMg neutron source. Referring to recent studies of thermal-pulse s-process models, we stress that a substantial amount of can survive the s process in spite of its enormously enhanced decay rate. The factual observation of at the surface of certain stars, therefore, does not necessarily contradict an s-process scenario with as a neutron source.
- Received 26 August 1985
DOI:https://doi.org/10.1103/PhysRevC.33.296
©1986 American Physical Society