Direct measurement of the ¹⁴⁰Ce(n,γ) cross section at kT  ≈ 11 keV

The neutron-capture reaction ¹⁴⁰Ce(n, γ ) is a key input for s -process nucleosynthesis due to its low capture probability, and has been discussed as a possible origin of the discrepancy between predicted and observed stellar cerium abundances. This discrepancy motivated a recent activation measurement at kT ≈ 34 keV and a time-of-flight (TOF) measurement, which reported conflicting Maxwellian-averaged cross sections (MACS), leading to large differences at the astrophysically relevant temperature of kT ≈ 8 keV. In this work, the ¹⁴⁰Ce(n, γ ) and ¹⁴²Ce(n, γ ) cross sections were measured using an activation technique with a quasi-Maxwellian neutron source at kT ≈ 11 keV, produced via the ¹⁸O(p,n) reaction. A ^natCe sample was irradiated at the PTB Ion Accelerator Facility, and the induced activities were measured by an ultra-low-background HPGe detector at the Felsenkeller underground laboratory. Cross sections were determined relative to the ¹⁹⁷Au(n, γ ) standard and used to derive MACS values. The resulting MACS of 22.2(1.2) mb at kT=10 keV is higher than the value previously adopted in stellar models, indicating that the observed ¹⁴⁰Ce abundance discrepancy is unlikely to originate from an overestimated neutron-capture cross section. The present result also provides a direct test of the widely used MACS extrapolation procedure from ∼ 30 keV to ∼ 8 keV and offers a unique insight into its reliability and potential limitations.