Isospin-breaking effects have been studied for the first time in $T=\frac{3}{2}$ isobaric analog states. Gamma decays have been observed from $T_z=-\frac{3}{2}$ nuclei, ${}^{49}\mathrm{Fe}$ and ${}^{53}\mathrm{Ni}$, presented here in new level schemes, and mirror energy differences have been computed following observation of analog states in ${}^{49}\mathrm{V}$ and ${}^{53}\mathrm{Mn}$, respectively. Shell-model calculations in the $\mathit{fp}$ shell are in good agreement with the data and reveal the importance of non-Coulomb isospin-breaking effects in $T=\frac{3}{2}$ isobaric analog states. A two-step fragmentation process was developed to allow access to highly proton-rich nuclei and to produce each member of a mirror pair via mirrored fragmentation of a ${}^{56}\mathrm{Ni}$ secondary beam. This work represents the first study using this technique and demonstrates the power of this approach for future studies of isobaric analog states in very proton-rich systems.

• Received 1 June 2009

DOI:https://doi.org/10.1103/PhysRevC.80.011306