Evidence for Collective Oblate Rotation inN=Z68Se

A $\gamma$-ray spectroscopic measurement of the $N=Z$ nucleus ${}^{68}\mathrm{Se}$ has been made following the ${}^{12}\mathrm{C}{(}^{58}\mathrm{Ni},2n)$ reaction at 185 and 220 MeV using Gammasphere and the Argonne Fragment Mass Analyzer. Despite a very low production cross section of $200\left(50\right)\mu \mathrm{b}$, two distinct rotational bands were found; the ground state band consistent with oblate collective rotation, and an excited band consistent with prolate rotation. These observations support long-standing predictions that nuclear ground states with substantial oblate $({\beta }_2\sim -0.3\mathrm{})$ deformation should exist in this region.