(n,gamma) cross-sections of light p nuclei

Abstract

The nucleosynthesis of elements beyond iron is dominated by the s and r processes. However, a small amount of stable isotopes on the proton-rich side cannot be made by neutron capture and is thought to be produced by photodisintegration reactions on existing seed nuclei in the so-called "p process". So far most of the p-process reactions are not yet accessible by experimental techniques and have to be inferred from statistical Hauser-Feshbach model calculations. The parametrization of these models has to be constrained by measurements on stable proton-rich nuclei. A series of (n,gamma) activation measurements on p nuclei, related by detailed balance to the respective photodisintegrations, was carried out at the Karlsruhe Van de Graaff accelerator using the (7)Li(p, n)(7)Be source for simulating a Maxwellian neutron distribution of kT = 25 keV. We present here preliminary results of our extended measuring program in the mass range between A = 74 and A = 132, including first experimental (n,gamma) cross-sections of (74)Se, (84)Sr, (120)Te and (132)Ba, and an improved value for (130)Ba. In all cases we find perfect agreement with the recommended MACS predictions from the Bao et al. compilation.