Stellar neutron capture cross sections of Nd, Pm, and Sm isotopes

The neutron capture cross sections of 146,148,150Nd have been determined 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 ⁷Li(p,n)⁷Be 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 around 6%, which represents a considerable improvement compared to previous measurements. These data are complemented by a new set of calculated cross sections for the unstable isotopes ¹⁴⁷Nd, 147,148,149Pm, and ¹⁵¹Sm, which act as branching points in the s-process path. Based on these results, the s-process flow in the Nd-Pm-Sm region is discussed with respect to the neutron density during stellar helium burning and to isotopic anomalies in meteorites. The updated s-abundances are also used for a discussion of r- and p-process residuals.