Isospin symmetry in the $T=1,A=62$ triplet

Abstract

Excited states in the $T_z=0,-1$ nuclei ${}^{62}$Ga and ${}^{62}$Ge were populated in direct reactions of relativistic radioactive ion beams at the RIBF. Coincident \grays were measured with the DALI2${}^{+}$ array and uniquely assigned to the $A=62$ isobars. In addition, ${}^{62}$Ge was also studied independently at JYFL-ACCLAB using the ${}^{24}$Mg(${}^{40}$Ca,$2n$)${}^{62}$Ge fusion-evaporation reaction. The first excited $T=1,J^{\ddot{I}}€=2^{+}$ states in ${}^{62}$Ga and ${}^{62}$Ge were identified at $979(1)$ and $965(1)$~keV, respectively, resolving discrepant interpretations in the literature. States beyond the first $2^{+}$ state in ${}^{62}$Ge were also identified for the first time in the present work. The results are compared with shell-model calculations in the $fp$ model space. Mirror and triplet energy differences are analyzed in terms of individual charge-symmetry and charge-independence breaking contributions. The MED results confirm the shrinkage of the $p$-orbits' radii when they are occupied by at least one nucleon on average.

aceepted Phys. Lett. B