Transition strengths and degree of deformation in 79Sr

High-spin states in {sup 79}Sr were studied using the {sup 54}Fe({sup 28}Si,2pn) reaction at 90 MeV, with a thick 14-mg/cm{sup 2} {sup 54}Fe target used to stop all recoils. Prompt {gamma}-{gamma} coincidences were detected using the Florida State University Compton-suppressed Ge array consisting of three Clover detectors and seven single-crystal detectors. The most recent {sup 79}Sr level scheme has been confirmed in three separate band structures up to a spin as high as the ((37/2){sup +}) yrast state based on {gamma}-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{sub 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{sub 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 conjunctionmore » with the cranked shell model. Lifetimes measured in a band based on the [431](1/2){sup +} intrinsic Nilsson configuration suggest a large quadrupole deformation ({beta}{sub 2}{approx_equal}0.41) associated with this band, providing another example of the strong deformation-driving properties of the d{sub 5/2} intruder orbital in the mass 80 region.« less