High-K structure in ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$

High-spin states in ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$ have been studied via the ${}_{}{}^{76}{}_{}{}^{}\mathrm{Ge}$(α,p2n) reaction. Proton-gated excitation functions extracted from measured γ-ray yields at beam energies of 32, 36, and 40 MeV and an additional γ-γ coincidence measurement at 40 MeV have been used to assign new γ-ray decay sequences to ${}_{}{}^{77}{}_{}{}^{}\mathrm{As}$. In particular, a positive-parity sequence up to spin 25/2 and a high-lying ΔI=1 sequence up to 21/2 and of probably negative parity have been found to decay into the known 9/$2^{+}$ isomer at 475.5 keV. Nuclear-shape calculations show a triaxial shape for the positive-parity states with moderate quadrupole deformation. The high-lying negative-parity sequence is interpreted as a high-K three-quasiparticle band similar to bands in adjacent nuclei. © 1996 The American Physical Society.