Shape changes and alignment properties inKr77

Abstract

Excited positive parity states up to spin ((41/2) have been studied in ${}_{}{}^{77}{}_{}{}^{}\mathrm{Kr}$ using a 98 MeV ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ beam on a natural chromium target. ΔJ=1 transitions have been identified throughout the positive parity band. The energies, mixing ratios, and B(M1) transition rates for these transitions alternate in size as the spin increases. A cranked shell model analysis was performed along with Strutinsky-Bogolyubov cranking calculations. The observed decrease in the signature splitting of the ν$g_{9/2}$ band has been attributed to a band crossing due to an aligning pair of $g_{9/2}$ protons. Prolate quadrupole deformations of ${\beta }_2$=0.34 for the one-quasiparticle band and ${\beta }_2$=0.26 for the three-quasiparticle band are predicted. This band crossing is associated with a shape change caused by the polarization effect of aligned quasiparticles.