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 ¹⁴⁰Ce 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 ¹³⁶Ce, ¹³⁸Ce, ¹⁴⁰Ce, and ¹⁴²Ce, were remeasured. A ⁿᵃᵗCe sample was irradiated with quasi-Maxwellian neutrons at $kT=34.2$ keV using the ⁷Li(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 ⁿᵃᵗCe neutron capture products were measured using a shielded high purity germanium detector. Cross sections were extracted relative to that of the ¹⁹⁷Au(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 ¹⁴⁰Ce a value ≈15% smaller than most recent experimental values.