Particle-hole and vibrational states in doubly closed subshell 96Zr from in-beam inelastic neutron and proton scattering

Abstract

Through in-beam (n, n′ γ) and (p, p′ γ) reaction studies, we have identified 33 levels in 96Zr and, from (n, n′) cross section and γ-ray angular distribution data, we have made spin-parity assignments for twenty of these levels. Recent DSAM nuclear level lifetimes were combined with electronic timing measurements in interpreting these states. The 1750 keV 2 + and 2439 keV 3 + states are suggested as the lowest neutron particle-hole multiplet, of ν(3 s 1 2 , 2 d 5 2 −) type, expected from the double closed subshell picture. On the other hand, the band built on the 1582 keV 0 + shape isomer is determined to have vibrational collectivity up to the two-phonon level. Candidates for two-phonon vibrational states of quadrupole-octupole and double octupole type, associated with the ground-state structure exhibiting octupole softness, are proposed.