Isomer production ratio of the Cd112(n,γ)Cd113 reaction in an s -process branching point

Abstract

A $\ensuremath{\beta}$-decay unstable isomer with a half-life of 14.1 yr at 264 keV in $^{113}\mathrm{Cd}$ is a branching point in the $s$ process, from which a weak branch reaches to a rare tin isotope $^{115}\mathrm{Sn}$ whose astrophysical origin has been an open problem. We have measured $\ensuremath{\gamma}$ rays decaying to the ground state or the isomer in the $^{112}\mathrm{Cd}(n,\ensuremath{\gamma})^{113}\mathrm{Cd}$ reaction using high-energy resolution detectors in conjunction with a time-of-flight method. The relative production ratios of the isomer to the total following the neutron capture reactions on $^{112}\mathrm{Cd}$ have been evaluated in an energy region of up to 9 keV, and the spin and parity of several resonances have been assigned.