Stellar s-process neutron capture cross section of Ce isotopes

Stellar abundances of cerium are of high current interest based both on\nobservations and theoretical models, especially with regard to the\nneutron--magic $^{140}$Ce isotope. A large discrepancy of $s-$process stellar\nmodels relative to cerium abundance observed in globular clusters was\nhighlighted, pointing to possible uncertainties in experimental nuclear\nreaction rates. In this work, the stellar neutron capture cross section of the\nstable cerium isotopes $^{136}$Ce, $^{138}$Ce, $^{140}$Ce, and $^{142}$Ce, were\nre-measured. A $^{nat}$Ce sample was irradiated with quasi-Maxwellian neutrons\nat $kT = 34.2$ keV using the $^{7}$Li($p,n$) reaction. The neutron field with\nan intensity of $3-5 \\times 10^{10}$ n/s was produced by irradiating the\nliquid-lithium target (LiLiT) with a mA proton beam at an energy (1.92 MeV)\njust above the threshold at Soreq Applied Research Accelerator Facility\n(SARAF). The activities of the $^{nat}$Ce neutron capture products were\nmeasured using a shielded High Purity Germanium detector. Cross sections were\nextracted relative to that of the $^{197}$Au(n,$\\gamma$) reaction and the\nMaxwellian-averaged cross section (MACS) of the Ce isotopes were derived. The\nMACS values extracted from this experiment are generally consistent with\nprevious measurements and show for $^{140}$Ce a value $\\approx 15$\\% smaller\nthan most recent experimental values.\n