Measurement of the 70Ge(n,¿) cross section up to 300 keV at the CERN n_TOF facility

Abstract

Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weakcomponent of the slow neutron capture processes, which occurs in massive stars. The (n,¿) cross section on70Ge, which is mainly produced in thesprocess, was measured at the neutron time-of-flight facility n_TOF atCERN. Resonance capture kernels were determined up to 40 keV neutron energy and average cross sectionsup to 300 keV. Stellar cross sections were calculated fromkT=5keVtokT=100 keV and are in verygood agreement with a previous measurement by Walter and Beer (1985) and recent evaluations. Average crosssections are in agreement with Walter and Beer (1985) over most of the neutron energy range covered, while theyare systematically smaller for neutron energies above 150 keV. We have calculated isotopic abundances producedins-process environments in a 25 solar mass star for two initial metallicities (below solar and close to solar).While the low metallicity model reproduces best the solar system germanium isotopic abundances, the close tosolar model shows a good global match to solar system abundances in the range of mass numbersA=60–80