COMPETING ANGULAR-MOMENTUM MECHANISMS AND NUCLEAR SHAPES AT HIGH-SPIN IN XE-122

Discrete gamma-ray transitions have been observed up to spin approximately 30 in 122Xe. A dramatic change in the mechanism by which this nucleus generates angular momentum is observed to occur above spin 20. The collective rotation of a prolate nucleus is replaced at high spin by a regime of non-collective single-particle states. Particularly favoured states are observed at high spin and by comparison with the predictions of the cranked Nilsson and Woods-Saxon models specific single-particle configurations are suggested. This gives information on the spectrum of single-particle states and the active orbitals which build high angular momentum states in this mass region.