Transition strengths and multiple band structure in 82Sr.

Abstract

High-spin states in $^{82}\mathrm{Sr}$ were studied using the $^{56}\mathrm{Fe}$${(}^{29}$Si,2pn) reaction at 95 MeV with a thick 78 mg/${\mathrm{cm}}^{2}$ natural Fe (92% $^{56}\mathrm{Fe}$) target. Prompt \ensuremath{\gamma}-\ensuremath{\gamma} coincidences were measured using three Compton-suppressed Ge detectors at 90\ifmmode^\circ\else\textdegree\fi{} relative to the beam and two at 30\ifmmode^\circ\else\textdegree\fi{}. Directional correlation of oriented nuclei ratios were determined from the 30\ifmmode^\circ\else\textdegree\fi{}-- 90\ifmmode^\circ\else\textdegree\fi{} coincidences to assist in assigning spin changes. Nine new states were found, along with 38 new transitions. The Doppler-shift attenuation method was used to determine the mean lifetimes of 22 states in $^{82}\mathrm{Sr}$. The continuum side feeding times into 10 states were determined by comparing the decay line shapes in coincidence with transitions above and below the state under study. The average transition quadrupole moment of 2.8(2) e b in the ground state band of $^{82}\mathrm{Sr}$ would correspond to a relatively large axial quadrupole deformation of ${\mathrm{\ensuremath{\beta}}}_{2}$=0.33, in agreement with theoretical predictions. The excited ${2}^{+}$ band has a higher moment of inertia but a lower transition quadrupole moment of 2.4(2) e b. In the negative-parity bands the quadrupole moment falls from about 3 to 2 e b with increasing spin.