No abstract

Gamma-ray transitions have been identified for the first time in "'W. The yrast hand has been established up to 28+(30+) and the alignment of the first pair of i,,/, neutmns is observed at a rotational frequency hw = 0.29 MeV. Above hw N 0.30 :vi e:' the h i pair of h,1/2 proions are observed io p.adudiy aiign with a strong interaction strength. The systematia of the neutron alignment in nuclei ranging from Dy to W and with neutron numben from 88 to 98 are discussed. The variations of alignment frequency with neutmn and proton number are explained in terms of changes in quadrupole and hexadecapole deformation and the changing position of the Fermi surf-in relatbn to the aligning neutron orbitals I ." .__.ll_ NUGLKAK K&ACIIUNY -rq-tiu,pznj. E("sCuj = 285 MeV; measured y-, coin, recoil (mass) coin. W; deduced levels. decays, E., E,. Enriched targets. array of escape suppwsed spectmmeters (Ge and EGO detectom), recoil separator. Systematics of first i1312 band crossing frequency for N = 88-98 and 2 = 66-74 nudei.

High-spin states were populated in 54122Xe68 using the fusion evaporation reaction 96Zr(30Si,4n) at a beam energy of 135 MeV. The level scheme of 122Xe has been extended up to spin approximately 30h(cross). The rotational bands and band crossings in 122Xe are assigned within the framework of the cranked shell model. Three bands are found to lose their rotational character or to branch above spin approximately 20h(cross). This is interpreted as the collective rotation of a prolate nucleus being replaced by a regime of non-collective single-particle states at high spin. Single-particle configurations are suggested for the high-spin non-collective states using modified oscillator and Woods-Saxon potentials. The development of the nuclear shape is analysed employing potential energy and total Routhian surface calculations.

Four, possibly five, superdeformed bands have been observed in '"^^Hg. Two of these bands have strikingly different dynamical moments of inertia from all previously observed superdeformed bands in this region. This behavior can be understood in terms of a level or band crossing. Evidence for transitions between two superdeformed bands is observed for the first time. This, together with the reduced alignments observed and the strong interaction between the crossing bands, is the first experimental evidence supporting the prediction for strong octupole correlations in superdeformed nuclei.