S-process nucleosynthesis in massive stars: new results on [sup 60]Fe, [sup 62]Ni and [sup 64]Ni

Abstract

The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n,γ) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives an overview on recent and future experiments for the Fe/Ni nucleosynthesis in massive stars. New results on 60Fe, 62Ni and 64Ni are reported. 60Fe is mostly produced during the short convective C shell burning phase, where peak densities of ∼1011 cm−3 are reached, prior to the SN explosion. The stellar (n,γ) cross section of 60Fe could be measured with a 1 μg sample obtained at PSI (Switzerlan...