Recoil-βtagging study of theN=Znucleus66As

An in-beam study has been performed to further investigate the known isomeric decays and to identify $T=1$ excited states in the medium-heavy $N=Z=33$ nucleus ${}^{66}$As. The fusion-evaporation reaction ${}^{40}$Ca(${}^{28}$Si,$pn$)${}^{66}$As was employed at beam energies of 75 and 83 MeV. The half-lives and ordering of two known isomeric states in ${}^{66}$As have been determined with improved accuracy. In addition, several prompt $\ensuremath{\gamma}$-ray transitions from excited states, both bypassing and decaying to the isomeric states in ${}^{66}$As, have been observed. Most importantly, candidates for the ${4}^{+}\ensuremath{\rightarrow}{2}^{+}$ and ${6}^{+}\ensuremath{\rightarrow}{4}^{+}$ transitions in the $T=1$ band have been identified. The results are compared with shell-model calculations using the modern JUN45 interaction in the $p{f}_{5/2}{g}_{9/2}$ model space.