Stellar s -process neutron capture cross section of Ce isotopes

Stellar abundances of cerium are of high current interest based both on observations and theoretical models, especially with regard to the neutron-magic Ce140 isotope. A large discrepancy of s-process stellar models relative to cerium abundance observed in globular clusters was highlighted, pointing to possible uncertainties in experimental nuclear reaction rates. In this work, the stellar neutron capture cross section of the stable cerium isotopes Ce136, Ce138, Ce140, and Ce142, were remeasured. A Cenat sample was irradiated with quasi-Maxwellian neutrons at kT=34.2 keV using the Li7(p,n) reaction. The neutron field with an intensity of 3-5×1010 n/s was produced by irradiating the liquid-lithium target (LiLiT) with a mA proton beam at an energy (1.92 MeV) just above the threshold at Soreq Applied Research Accelerator Facility (SARAF). The activities of the Cenat neutron capture products were measured using a shielded high purity germanium detector. Cross sections were extracted relative to that of the Au197(n,γ) reaction and the Maxwellian-averaged cross section (MACS) of the Ce isotopes were derived. The MACS values extracted from this experiment are generally consistent with previous measurements and show for Ce140 a value ≈15% smaller than most recent experimental values.