The high-spin decay of 71 Se was studied using the 54 Fe( 23 Na,αpn) reaction at 80 MeV and the Florida State University Compton-suppressed Ge array consisting of three clover detectors and seven single-crystal detectors. Based on prompt γ -γ coincidences measured in the experiment, the known level scheme was enhanced and extended to higher spin with 19 new transitions. A band that was previously suggested to have positive parity was reassigned as the "missing" signature partner of an existing negative-parity band. Spins were assigned based on directional correlation of oriented nuclei ratios. Lifetimes of 17 excited states were measured using the Doppler-shift attenuation method. Experimental Q t values imply an intermediate degree of collective behavior for 71 Se at high spin. Theoretical Q t values determined from cranked Woods-Saxon (CWS) calculations show better agreement with the experimental ones for the positive-parity states than the negative-parity states. Shape competition and γ softness characterize the low-spin states of the lowest positive-and negative-parity bands based on the CWS calculations. At high spin, triaxial shapes with γ > 0 • are predicted.

High-spin states in 71 As were studied using the 54 Fe( 23 Na,α2p) reaction at 80 MeV. Prompt γ -γ coincidences were measured using the Florida State University Compton-suppressed Ge array consisting of three clover detectors and seven single-crystal detectors. The existing high-spin level scheme has been verified, and 21 new transitions have been added based on an investigation of weak γ -ray coincidence relations and relative γ -ray intensities. Lifetimes of 16 excited states were measured using the Doppler-shift attenuation method applied to the experimental line shapes of decays in all of the known rotational bands. The B(E2) strengths inferred from the lifetimes indicate that moderate to high collective behavior persists to the highest observed spins in the lowest positive-and negative-parity bands, in qualitative agreement with projected shell-model calculations. The band suggested to be based on the πf 7/2 orbital shows a similar degree of collectivity within the same spin range, with B(E2) values in good agreement with those predicted by the projected shell model assuming a constant prolate deformation of 2 = +0.27. The experimental Q t values in this band are somewhat smaller than predicted by cranked Woods-Saxon calculations.

High-spin states in 79 Sr were studied using the 54 Fe( 28 Si,2pn) reaction at 90 MeV, with a thick 14 mg/cm 2 54 Fe target used to stop all recoils. Prompt γ − γ coincidences were detected using the FSU Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. The most recent 79 Sr level scheme has been confirmed in three separate band structures up to a spin as high as the ( 37 2 + ) yrast state based on γ-ray coincidence relations, intensity and effective lifetime measurements, and directional correlation of oriented nuclei ratios. Lifetimes of 33 excited states were measured using the Doppler-shift attenuation method, with the experimental line shapes obtained at two separate observation angles and by gating from above the transitions of interest whenever possible. Transition quadrupole moments Q t inferred from the lifetimes indicate a high degree of collectivity and deformation over a rather wide range of spins in all three observed bands, with evidence for modest reductions in the values with increasing spin. The changes in Q t are attributed to the onset of quasiproton alignment and are supported qualitatively by the predictions of the projected shell model and cranked Woods-Saxon calculations in conjunction with the cranked shell model. Lifetimes measured in a band based on the [431] 1 2 + intrinsic Nilsson configuration suggest a large quadrupole deformation (β 2 ≈ 0.41) associated with this band, providing another example of the strong deformation-driving properties of the d 5/2 intruder orbital in the mass 80 region.