Negative-parity structures and lifetime measurements in [sup 71]As

High-spin states up to (29/2[sup +]) and (29/2[sup [minus]]) in [sup 71]As have been studied via the [sup 58]Ni([sup 19]F,[alpha]2[ital p]) reaction at 62 MeV using in-beam [gamma]-ray spectroscopic techniques. Based on a particle-[gamma] coincidence measurement a new decay sequence of negative parity has been assigned to [sup 71]As. Lifetimes for some [ital E]2 transitions were extracted from Doppler-shifted line shapes observed in coincidence mode, and experimental transition quadrupole moments were determined. They indicate a moderate to high collectivity in both the positive-parity yrast band and the new negative-parity decay sequence at high spins. Total Routhian surfaces calculated for states of both parities reveal strong triaxial shapes at high spins. A noncollective structure of 19/2[sup ([minus])] and 21/2[sup ([minus])] states is interpreted as a three-quasiparticle excitation.