Abstract
High-spin states have been populated in using the Mg,4nγNd reaction. Several rotational bands have been observed based on two- and four-quasiparticle configurations. The ground-state band backbends sharply at a frequency ħω=0.34 MeV due to the alignment of a pair of protons. Both signatures of a negative parity side band based on a π⊗π configuration were observed to backbend at a frequency ħω=0.44 MeV, again due to the alignment of a pair of protons. All these bands are prolate because of the stabilizing influence of the quasiprotons on the γ-soft core. In addition to the proton alignment in the ground-state band, a rotational band is observed built on a second state, which involves the alignment of a pair of neutrons. An alignment of neutrons from the upper midshell drives the nucleus towards a collectively rotating oblate (γ=-60°) shape. Both signatures of a band based on a ν⊗ν configuration were observed, also possibly oblate. The observation of both neutron and proton low-frequency alignments is consistent with cranked-shell model calculations and theoretical estimates of the prolate-oblate energy difference for this nucleus.
- Received 20 February 1987
DOI:https://doi.org/10.1103/PhysRevC.36.153
©1987 American Physical Society