Stellar neutron capture cross sections of the Xe isotopes

Abstract

The (n,γ) cross sections of the important s-process nuclei 1 2 8 Xe, 1 2 9 Xe, and 1 3 0 Xe have been measured for the first time in the astrophysically relevant neutron energy range from 3 to 225 keV. Neutrons were produced via the 7 Li(p,n) 7 Be reaction by bombarding metallic Li targets with the pulsed proton beam of the Karlsruhe 3.7 MV Van de Graaff accelerator. Highly enriched Xe gas samples in thin-walled titanium spheres were used in the experiment, and capture events were registered with the Karlsruhe 47r Barium Fluoride Detector. The cross sections were determined relative to the gold standard with overall uncertainties of 1.5 - 2.5% over most of the investigated energy range. From these results Maxwellian averaged stellar (n,γ) cross sections with typical uncertainties of 2% were calculated for thermal energies between kT = 8 keV and 100 keV. In contrast to previous theoretical estimates, which were known to exhibit uncertainties of 30 to 50%, this work provides a reliable basis for quantitative astrophysical analyses.