Photoneutron cross sections for samarium isotopes: Toward a unified understanding of(γ,n)and(n,γ)reactions in the rare earth region

Abstract

Photoneutron cross sections were measured for the seven stable samarium isotopes ${}^{144,147,148,149,150,152,154}\mathrm{Sm}$ near the neutron threshold with quasi-monochromatic laser-Compton scattering $\ensuremath{\gamma}\phantom{\rule{0.28em}{0ex}}\mathrm{rays}$. Our photoneutron cross sections are found to be low by 20%--37% relative to existing data. The photoneutron data are analyzed with the talys reaction code by considering the Skyrme Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random phase approximation (QRPA) model and the axially symmetric deformed Gogny HFB plus QRPA model of the $E1$ $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{ray}$ strength. Using the $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{ray}$ strength function constrained by the present photoneutron data, we made a thorough analysis of the reverse $(n,\ensuremath{\gamma})$ cross sections including the radioactive nucleus $^{151}\mathrm{Sm}$ with a half-life of 90 yr. The radiative neutron capture cross section for $^{153}\mathrm{Sm}$ with the half-life of 1.928 d is deduced with the $\ensuremath{\gamma}\text{\ensuremath{-}}\mathrm{ray}$ strength function method.