ROTATIONAL BANDS IN CE-135 - COLLECTIVE PROLATE AND OBLATE ROTATION

Several rotational bands have been established in the N=77 Ce135 nucleus following the Sn122(18O,5n) reaction. At low spins, the yrast band, built on an orbital from the top of the h11/2 shell, exhibits a large signature splitting of 300 keV implying a significant deviation from axial symmetry (0°). At higher spins, three I=1 bands were established. Two of these bands are built on prolate (0°) mixed neutron-proton configurations as systematically observed in several N=75 isotones. The third of these bands shows properties similar to those observed for collectively rotating (-60°) mixed neutron-proton configurations as recently reported in nearby odd-Z, doubly odd, and even-even nuclei. The present study represents the first observation of such a band in an odd-N nucleus. In addition, two decoupled I=2 bands, built on oblate three-quasineutron configurations, were observed. © 1990 The American Physical Society.