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K isomers are studied in Pu and Cm isotopes, and also in Hf and W nuclei. Many high-K states, several of which are isomeric, are identified. Lifetime measurements spanning the ns-s range have been performed, and decay paths of isomers established. Rotational bands built on high-K states are also identified in many cases. Isomer decays are considerably hindered in many instances, both in the A≈180 and 250 regions indicating that Kis an approximately conserved quantum number. High- K states become the favored excitation mode at high spins in the A≈180 region. The energies of 2-quasiparticle high-K states in Cm isotopes suggest the presence of a deformed subshell gap at N=152. [ABSTRACT FROM AUTHOR]

Spectroscopic studies of nuclei in the A∼250, Z∼100 region provide critical input to theoretical models that attempt to describe the structure and stability of the heaviest elements. We report here on new spectroscopic studies in the N = 150,151 nuclei 244,245Pu. (Z = 94). Excitations in these nuclei on the neutron-rich side of the valley of stability, accessed via inelastic and transfer reactions, complement fusion-evaporation studies of Z≥100 nuclei. States in 244,245Pu were populated using 47Ti and 208Pb beams incident on a 244Pu target, with delayed and prompt gamma rays detected by the Gammasphere array. The new results are discussed in the context of emerging systematics of one- and two-quasiparticle excitations in N≥150 nuclei. [ABSTRACT FROM AUTHOR]

The talk will focus on spin-dependent competition between oblate and prolate shape minima in the potential energy landscape of 180Hf (the most neutron-rich stable isotope), mediated via the alignment of valence nucleons. Results of a prompt spectroscopic study, using deep inelastic reactions with Gammasphere and CHICO, bombarding a thin 232Th target with a 180Hf beam ∼25% above the Coulomb barrier, will be presented. Nucleon alignments in both prolate and oblate minima will be discussed, as well as the favoring of oblate collective rotation at high spins, observed through a mixing with gamma vibrations built on the prolate shape. [ABSTRACT FROM AUTHOR]

High-K states in the region of 177Lu have been studied using multi-nucleon transfer reactions with 136Xe beams and Gammasphere. Results include identification of the predicted 5-quasiparticle Kπ = 39/2 - isomer in 177Lu, a 7-quasiparticle Kπ = 49/2 + isomer in 179Ta with an anomalously fast decay, and numerous other examples in a range of Yb close to stability. The results are discussed in the context of the expectations for multi-quasiparticle states near Z = 72 and the factors which may both govern isomer formation and also give an insight into K-purity, specifically chance degeneracies, and statistical mixing above the yrast line. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]