(n,γ) cross sections of light p-nuclei. Towards an updated experimental database for the p-process

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. Those 32 stable, proton-rich isotopes between 74Se and 196Hg are 10 to 100 times less abundant than the respective s and r nuclei. They are produced in the so-called γ or p process, where proton-rich nuclei are made by sequences of photodisintegrations and β+ decays. In this scenario, pre-existing seed nuclei from the s and r processes are destroyed by photodisintegration in a high-temperature environment. 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 of stable proton-rich nuclei. A series of (n,γ) activation measurements, related by detailed balance to the respective photodisintegrations, where carried out at the Karlsruhe Van de Graaff accelerator using the 7Li(p,n)7Be source. The status quo of (n,γ) rates for the 32 p nuclei is presented. Experimental data is available for 20 isotopes. Our comprehensive measuring campaign focusses on the mass range A = 70-140 and includes the first results for the missing stellar cross sections of 74Se, 84Sr, 102Pd, 120Te and 132Ba. Furthermore, we plan to improve the accuracy of 92,94Mo, 98Ru, 113In and 130Ba. The aim of this work is the creation of an Online Library for experimental p-process cross sections and reaction rates. (author)