Anomalous52+States inSe77from the Decay of 56-hBr77

Abstract

The levels in ${}_{}{}^{77}{}_{}{}^{}\mathrm{Se}$ from the decay of 56-h ${}_{}{}^{77}{}_{}{}^{}\mathrm{Br}$ were investigated. From singles measurements of the $\gamma$-ray energies and intensities employing a high-resolution Ge(Li) detector, and from coincidence relationships determined in $\gamma -\gamma$ coincidence measurements using two Ge(Li) detectors, it was established that levels at 161.9, 238.9, 249.7, 301.1, 439.5, 520.7, 581.2, 682.3, 752.2, 818.2, 824.8, 911.9, 1005.6, and 1187.5 keV are populated in the decay of 56-h ${}_{}{}^{77}{}_{}{}^{}\mathrm{Br}$. From present $log\mathrm{ft}$ values and $K$-shell conversion coefficients, and from previously reported ($d,p$) and ($d,t$) reaction data, many $J^{\pi }$ values were assigned. The level structure of the anomalous ${\frac{5}{2}}^{+}$ and ${\frac{7}{2}}^{+}$ states is compared with recent calculations on the pairing-plus-quadrupole model extended to include higher shell-model orbits, with satisfactory qualitative agreement between experiment and theory.