NEUTRON EXCITATIONS ACROSS THE N = 86 SUPERDEFORMED SHELL GAP

Based on data obtained with the Eurogam spectrometer, a systematic inv estigation of superdeformed bands built on single neutron excitations across the N = 86 shell gap has been carried out for gadolinium, terbi um, and dysprosium isotopes with 85 less-than-or-equal-to N less-than- or-equal-to 87. In each nucleus, pairs of bands corresponding to degen erate signature partners have been observed. The effective alignment i s constant and close to zero for many of the bands, in agreement with cranked shell model calculations for the [402]5/2 and [514]9/2 orbital s. Several bands exhibit non-zero alignments, indicating in some cases the influence of pairing correlations even at high spin and in other cases the occupancy of the [521]3/2 orbital.