High-spin states in ${}^{77}$Kr were identified via analysis of prompt $\gamma$-$\gamma$ coincidences in the ${}^{58}$Ni${(}^{29}$Si,$2\alpha 2p)$ reaction at 128 MeV at the Gammasphere facility. Evaporation channel selection was achieved using the 95 element Microball charged-particle detector. 27 new states and 42 new transitions were found. The positive-parity bands were confirmed and the $\alpha =-$$\frac{1}{2}$ band extended to ${\frac{39}{2}}^{+}$. The negative-parity signature pair was extended to ${\frac{31}{2}}^{-}$ and ${\frac{37}{2}}^{-}$. Two new high-lying negative-parity bands were found extending from a state of spin $I=$$\frac{15}{2}$ and energy 2.6 MeV to 17.4 MeV at $I=\left(\frac{55}{2}\right)$. The new bands appear highly deformed and become yrast at high spin. A three-quasiparticle structure based on deformation driving, low-$K$ unique-parity and intruder orbitals is suggested for them.

• Received 4 April 1997

DOI:https://doi.org/10.1103/PhysRevC.56.772