Electric and magnetic $\gamma$-ray strength functions at finite-temperature

Abstract

The $\gamma$-ray strength function ($\gamma$SF) is essential for understanding the electromagnetic response in atomic nuclei and modeling astrophysical neutron capture rates. We introduced a microscopic description of both electric dipole (E1) and magnetic dipole (M1) $\gamma$SFs that includes finite-temperature effects within relativistic density functional theory. The temperature dependence of the total electromagnetic $\gamma$SFs shows significant modification in the low-energy region due to thermal unblocking effects, essential for agreement with recent particle-$\gamma$ coincidence data from the Oslo method. An investigation of the electric and magnetic contributions to the total $\gamma$SF in hot nuclei indicates that the M1 mode becomes more prominent in the low-energy region, different than what is known at zero temperature. This microscopic approach offers new insights into the interplay between E1 and M1 $\gamma$SFs at finite-temperature, and opens new perspectives for future studies of $(n,\gamma)$ reactions and nucleosynthesis in hot stellar environments.