High-spin levels and band structure inKr78

The high-spin states of ${}_{}{}^{78}{}_{}{}^{}\mathrm{Kr}$ have been studied through observation of $\gamma$ rays emitted from the ${}_{}{}^{68}{}_{}{}^{}\mathrm{Zn}({}_{}{}^{12}{}_{}{}^{}\mathrm{C},2n)$ reaction produced with projectile energies of 33-38 MeV. The energies, relative intensities, angular distributions, and linear polarizations of the $\gamma$ rays were measured. Lifetimes of states were obtained from the Doppler broadening of the $\gamma$-ray peaks. Many of the levels appear to belong to one of three bands: (1) the ground-state band with energy spacing between that given by the pure rotational and vibrational models, (2) a band built on a $5^{-}$ state which is ascribed to rotational alignment of two quasiparticles, one of which is in a $g_{\frac{9}{2}}$ orbital, and (3) a $\Delta J=1\mathrm{}$ band which has characteristics of a $\gamma$-vibrational band in a deformed nucleus. There is evidence for the beginning of a fourth band built on a $J=6\mathrm{}$ level.