Measurement of weak rates for stellar evolution via the (t,3He) reaction

The (t,3He) charge-exchange reaction has been developed as a tool to extract Gamow-Teller strengths on nuclei of importance for stellar evolution. A secondary triton beam of 115 MeV/nucleon is used, either produced from a primary α beam, or, since recently, from a primary 16O beam. Here, the (t,3He) reaction is used to study the Gamow-Teller strength distribution in 58Co via the 58Ni(t,3He) reaction. The experimental results are compared with calculations in large-scale shell models using the kb3g and gxpf1 interactions, as well as existing data from 58Ni(n, p) and 58Ni(d,2He) experiments. The differences between the data and theoretical models are studied in terms of electron-capture rates in the pre-collapse stages of core-collapse supernovae.