DOE OSTI2019
Improving our understanding of the origin of the elements in the observable universe as well as the nature of the environments responsible for their production has been of paramount importance to the nuclear physics community. More than half of the isotopes of these elements are created via neutron-capture processes, and thus accurate measurements of the salient underlying nuclear physics, such as neutron-capture cross sections, masses, and β-decay half-lives are crucial. Of particular signifcance to the synthesis of isotopes in the mass range of A ≈ 60 to A ≈ 90, via the weak s process, are the neutron-capture cross sections of 63,65 Cu, where large discrepancies between measurements exist. Recent measurements have addressed these discrepancies for 63 Cu [Weigand et al., Phys. Rev. C 95, 015808 (2017)], but questions still remain for 65 Cu. Here, we report a new measurement of the 65Cu(n, γ ) cross section performed using the Detector for Advanced Neutron Capture Experiments located at the Los Alamos Neutron Science Center of Los Alamos National Laboratory. The Maxwellian-averaged cross section (MACS) for 65 Cu(η, γ) at $kT$ = 30 keV deduced from this work is (37.0 ± 0.3 stat. ± 3.3 sys. ) mb. The impact on weak s-process nucleosynthesis of new MACS values, calculated over the range of kT = 5 to 100 keV, for 65 Cu, combined with the updated MACS for 63 Cu [Weigand et al., Phys. Rev. C 95, 015808 (2017)] and 63 Ni [Weigand et al., Phys. Rev. C 92, 045810 (2015)], were investigated. Findings of this investigation show an increase of predicted nucleosynthesis yields of elements of Zn to Zr by as much as 20%.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗