High resolution neutron capture and transmission measurements on137Baand their impact on the interpretation of meteoric barium anomalies

Abstract

We have made improved measurements of the neutron capture and total cross sections for ${}^{137}\mathrm{Ba}$ over a sufficiently wide range of energies so that the reaction rate at $s$-process temperatures ($\mathrm{kT}$=6--23 keV) can be determined solely from the data. These rates are crucial for the interpretation of recently discovered anomalies of Ba isotopes in silicon carbide grains from the Murchison meteorite. Recent stellar models of the $s$ process are in agreement with the meteoric anomaly data for Ba only if the ${}^{137}\mathrm{Ba}(n,\ensuremath{\gamma})$ reaction rate is 20% larger than the previously accepted rate. Our reaction rates at $s$-process temperatures are in agreement with the extrapolated reaction rate from the most recent previous measurement. Hence, our results uphold, and place on much firmer footing, the discrepancy between recent stellar models of the $s$-process and the meteoric anomaly data.