High-spin spectroscopy and shell-model interpretation of the N < 126 radium isotopes ${}^{212}$Ra and ${}^{213}$Ra

Abstract

The level structures of ${}^{212}$Ra and ${}^{213}$Ra have been established via time-correlated $\gamma$-ray spectroscopy following the ${}^{204}$Pb(${}^{12}$C,4$n$)${}^{212}$Ra and ${}^{204}$Pb(${}^{13}$C,4$n$)${}^{213}$Ra reactions. In ${}^{212}$Ra, levels up to $\sim 6.2$ MeV were identified and firm spin-parity assignments were achieved to a $J^{\pi }=19^{+}$ isomer with a mean life of 31(3) ns. For ${}^{213}$Ra the corresponding values were $\sim 4.5$ MeV in excitation energy and $J^{\pi }=33/2^{+}$. Two isomeric states with $J^{\pi }=23/2^{+}$, $\tau =27(3)$ ns and $J^{\pi }=33/2^{+}$, $\tau =50(3)$ ns were discovered in ${}^{213}$Ra. The experimental data were compared with semiempirical shell-model calculations, which allowed dominant configurations to be assigned to most of the observed levels.

22 pages, 12 figures