New isomer ${}_{}{}^{32}{}_{}{}^{}\mathrm{Al}_{}^m{}_{}{}^{}$

A new isomer in the neutron-rich isotope ${}_{}{}^{32}{}_{}{}^{}\mathrm{Al}$ has been identified among the fragmentation products of beams of $75A$ MeV ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$ and $61A$ MeV ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$ using the LISE spectrometer at GANIL. The population of an isomeric state was inferred from the detection of $\gamma$ radiation following the decay of an implanted ${}_{}{}^{32}{}_{}{}^{}\mathrm{Al}$ fragment. A half-life for ${}_{}{}^{32}{}_{}{}^{}\mathrm{Al}_{}^m{}_{}{}^{}$ of 200(20) ns was measured, and an excitation energy of 956 keV deduced from the observed $\gamma$-ray cascade. Shell model calculations provide a candidate for the isomer, having $J^{\pi }=4^{+}$. However, this association reveals a rare inversion of low-energy levels by the Wildenthal's "universal" $\mathrm{sd}$-shell (USD) interaction, extending to the $N=19\mathrm{}$, $Z=13\mathrm{}$ range of USD anomalies (previously identified for $N=20\mathrm{}$, $Z=11, 12$ linked to the vanishing of the $N=20\mathrm{}$ shell gap.