Neutron capture cross sections of the cerium isotopes for s- and p-process studies

The neutron capture cross sections of the stable cerium isotopes 136, 138, 140, and 142 have been measured relative to that of gold by means of the activation method. The samples were irradiated in a quasistellar neutron spectrum for kT = 25 keV using the Li-7(p,n)Be-7 reaction near threshold. Variation of the experimental conditions in different, activations and the use of different samples allowed for the reliable determination of corrections and the evaluation of systematic uncertainties. The resulting stellar cross sections can be given with uncertainties between 3% and 7%. The present data for Ce-136 and Ce-138 are the first experimental information in this mass region of relevance for p-process studies to our knowledge, whereas the new Ce-142 cross section allowed to resolve a previous discrepancy. The experimental results are complemented by a set of calculated cross sections for all cerium isotopes from Ce-132 to Ce-142 as well as for Pr-142, Pr-142, and Pr-143. The improved cross sections were used in an updated s-process analysis of the Ce-Pr-Nd region that included the small branchings at Ce-141 and Pr-142. The consequences of the resulting s abundances are discussed with respect to isotopic anomalies in meteoritic neodymium as well as for the r- and p-process residuals.