High spin states in ${}_{}{}^{79}{}_{}{}^{}\mathrm{Sr}$ were populated via the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mg}$,2pn) at 80 and 85 MeV beam energy. Twelve lifetimes in the range from 0.5 to 150 ps and four lifetime limits were measured with Doppler-shift methods. By comparing lifetimes in ${}_{}{}^{79}{}_{}{}^{}$,80,82Sr obtained with the recoil distance and Doppler-shift attenuation methods, the appropriate electronic stopping power of Sr ions recoiling in Ta was determined. In addition, lifetimes of yrast states in ${}_{}{}^{80}{}_{}{}^{}\mathrm{Sr}$ and ${}_{}{}^{79}{}_{}{}^{}\mathrm{Rb}$ were determined in the concurrent reactions ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mg}$,2p) and ${}_{}{}^{58}{}_{}{}^{}\mathrm{Mg}$,3p). The ΔI=2 E2 transition strengths and the E2/M1 mixing ratios of the ΔI=1 transitions in ${}_{}{}^{79}{}_{}{}^{}\mathrm{Sr}$ confirm the picture of extremely prolate deformed rotational bands (${\beta }_2$≊0.42), based on the [301]${(3/2\mathrm{}}^{\mathrm{-}}$ and [422]${(5/2\mathrm{}}^{+}$ Nilsson orbits. A reduction in B(E2) values is observed at the onset of (3qp) alignment. The band structure of ${}_{}{}^{79}{}_{}{}^{}\mathrm{Sr}$ is discussed in terms of the cranked shell and the Woods-Saxon cranking model with pairing.

• Received 2 May 1989

DOI:https://doi.org/10.1103/PhysRevC.41.603