Electromagnetic transition strengths between high spin states inSr79andSr80

Abstract

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 \ensuremath{\Delta}I=2 E2 transition strengths and the E2/M1 mixing ratios of the \ensuremath{\Delta}I=1 transitions in $^{79}\mathrm{Sr}$ confirm the picture of extremely prolate deformed rotational bands (${\ensuremath{\beta}}_{2}$\ensuremath{\approxeq}0.42), based on the [301]${(3/2}^{\mathrm{\ensuremath{-}}}$ and [422]${(5/2}^{+}$ 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.