Four-valence-proton yrast states in 1 6850Er82

The level structure of the four-valence-proton N = 82 nucleus 150Er has been studied by γ-ray spectroscopy following reactions of 225--255 MeV /sup 58,60/Ni beams on /sup 92,94,95/Mo and 93Nb targets. Yrast levels in 150Er are established up to 9.5 MeV excitation energy; they include isomeric levels at 2797, 7372, and 9509 keV. The observed levels up to 5222 keV are interpreted in terms of shell model configurations involving the four valence protons outside the 146Gd core. They include states with dominant seniority two and four configurations πh/sub 11/2/4, πh/sub 11/2/3s/sub 1/2/, and πh/sub 11/2/3d/sub 3/2/, and octupole excitations. The levels above 5222 keV must involve excitation of the 146Gd core, and they are not interpreted in detail. The energies of the πh/sub 11/2/4 levels are found to agree reasonably with predictions based on empirical two-body interactions taken from the πh/sub 11/2/2 spectrum of 148Dy. Even better agreement is obtained by taking account also of the known πh/sub 11/2/3 energies in 149Ho. The dependence of E2 transition probabilities in N = 82 nuclei on the πh/sub 11/2/ subshell occupation number is discussed