In-beam γ-ray spectroscopy of Ac211,213 and Ra211

Abstract

The first in-beam $\gamma$-ray spectroscopic study of the neutron-deficient actinium isotopes ${}^{211,213}\mathrm{Ac}$ has been carried out at the Accelerator Laboratory of the University of Jyväskylä using a highly selective recoil-decay tagging method with the jurogam 3 germanium-detector array and MARA separator. The nuclei of interest were produced using the ${}^{175}\mathrm{Lu}({}^{40}\mathrm{Ar},4n){}^{211}\mathrm{Ac}$ and ${}^{180}\mathrm{Hf}({}^{37}\mathrm{Cl},4n){}^{213}\mathrm{Ac}$ fusion-evaporation reactions. Excited states in ${}^{211}\mathrm{Ac}$ were observed for the first time. In ${}^{211}\mathrm{Ac}$ and ${}^{213}\mathrm{Ac}$ low-lying core-excited states whose excitation energies follow the systematic trends of their respective core states in even-even isotones ${}^{210}\mathrm{Ra}$ and ${}^{212}\mathrm{Ra}$ were identified. Additionally, we were able to extend the level scheme of ${}^{211}\mathrm{Ra}$, which was also produced in the ${}^{40}\mathrm{Ar}+{}^{175}\mathrm{Lu}$ reaction. We also remeasured the half-lives of the ground states of these nuclei and also that of the (${{}^{13}{/}_2}^{+}$) isomeric state of ${}^{211}\mathrm{Ra}$.