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Isomers and high-spin structures with rotation-aligned oblate configurations have been studied in several Pt isotopes. The 12+ states in the even Pt isotopes from 192-198Pt are found to be metastable, and have (i13/2)2 neutron character. The progression of E2 transition probabilities from the 12+ to 10+ states across the Pt isotopic chain implies reduction in collectivity, followed by an abrupt decrease at N=120 (198Pt). This behavior is quite distinct from the gradual decrease of B(E2) values near the respective ground states. A large contribution from aligned angular momentum, to the rotational sequences built on the 12+ states, is visible. This is due to the relatively small crossing frequencies for nucleons in low-Ω orbitals at oblate deformation in comparison to higher values for prolate shapes. As a result, oblate rotation is found to be increasingly favored for higher neutron numbers. [ABSTRACT FROM AUTHOR]

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]

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]