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Configuration-constrained potential-energy-surface calculations have been performed to investigate multiquasiparticle high-if states built on superdeformed minima in 192,194,196Pb and 198Po. The calculations predict that 196Pb and 198Po would be favorable candidates for the observation of low-lying superdeformed two- and four-quasiparticle high-K states. The possible decay paths and lifetimes that could lead to isomers are evaluated in detail for 196Pb. Comparisons between the predictions and previous observations of octupole-vibrational excitations indicate also that bands built on superdeformed high-K intrinsic states may compete with the octupole-vibrational mode in this mass region. The quadrupole moments of both the collective and intrinsic excitations are analyzed. [ABSTRACT FROM AUTHOR]

Configuration-constrained potential-energy-surface calculations are performed including ß6 deformation to investigate high-K" isomeric states in nuclei around 254No and 270Ds, the heaviest nuclei where there have been some observations of two-quasiparticle isomers, while data for four-quasiparticle isomers are scarce. We predict the prevalent occurrence of four-quasiparticle isomeric states in these nuclei, together with their favored configurations. The most notable examples, among others, are Kπ = 20+ states in 266-268DS and 268,270Cn having very high K value, relatively low excitation energy, and well-deformed axially symmetric shape. The predicted isomeric states, with hindered spontaneous fission and a decay, could play a significant role in the future study of superheavy nuclei. [ABSTRACT FROM AUTHOR]

The neutron-rich zirconium isotopes are a key testing ground for nuclear models due to their sensitivity to shape changes, and because they cross the r-process path of explosive nucleosynthesis. Furthermore, recent experimental data have revealed a high-spin isomer in l08Zr. Here we report the results of configuration-constrained potential-energy-surface calculations of ground states and high-K states in 104-110Zr, restricted to quadrupole and hexadecapole shapes. These calculations enable the existing isomer data to be understood, and predictions are made for 110Zr. [ABSTRACT FROM AUTHOR]

Excited states in the N = 102 isotones 166Gd and 164Sm have been observed following isomeric decay for the first time at RIBF, RIKEN. The half-lives of the isomeric states have been measured to be 950(60) and 600(140) ns for 166Gd and 164Sm, respectively. Based on the decay patterns and potential energy surface calculations, including β6 deformation, a spin and parity of 6- has been assigned to the isomeric states in both nuclei. Collective observables are discussed in light of the systematics of the region, giving insight into nuclear shape evolution. The decrease in the ground-band energies of 166Gd and 164Sm (N = 102) compared to 164Gd and 162Sm (N = 100), respectively, presents evidence for the predicted deformed shell closure at N = 100. [ABSTRACT FROM AUTHOR]

Deep-inelastic reactions and γ-ray spectroscopy have been used to study excited states in 195Au. A three-quasiparticle isomer with a mean-life of 18.6(3) µs has been assigned at 2461 + Δ keV, with decays into newly identified structures. Possible configurations for the isomer are discussed including a Jπ = 31/2- intrinsic state produced by coupling the 11/2- [505] proton hole to the 10+ state obtained from the 9/2+ [624], 11/2+ [615] two-neutron holes, expected from configuration-constrained potential-energy-surface calculations. Residual interactions are evaluated within a semi-empirical shell model basis. New lifetime information is also obtained for the 21/2+ and 25/2+ states at 1813 and 1980 keV. The relationship between these and other newly identified states and the negative-parity states in the even-even neighbors is discussed. [ABSTRACT FROM AUTHOR]

Excited states in 55V and 55Cr have been populated via pn and 2n evaporation channels, respectively, following the fusion of a 48Ca beam at 172 MeV with a 9Be target. Level schemes have been deduced for the two nuclides to excitation energies of 7467 (55V) and 12226 keV (55Cr), with spins of 27/2+ and 33/2+, respectively. Negative-parity states are compared with shell-model calculations using three different effective interactions in the full fp model space. Negative-parity levels of 55Cr are explained in terms of single-particle fp-shell configurations outside N = 28 and N = 32 cores. Positive-parity states in both isotopes show evidence for the involvement of neutron g9/2 configurations. In the case of 55Cr, a quasirotational structure based on the 1/2+[440] Nilsson orbital is observed up to the terminating state. In 55V, positive-parity states do not exhibit well-developed collective features, and the observation of octupole decays is an indication of their importance in transitions from neutron g9/2 configurations to the fp shell. Experimental results are compared with the predictions of a traditional shell model, the projected shell model, and total-Routhian-surface calculations. [ABSTRACT FROM AUTHOR]

Nd was produced by irradiation of an enriched target of Ru with a Ar beam and studied by using a helium-jet fast tape transport system in combination with X- $ \gamma$ and $ \gamma$ - $ \gamma$ coincidence measurements. A 2.6s isomer of Nd was observed for the first time and tentatively proposed to be the configuration of 1/2[411]. [ABSTRACT FROM AUTHOR]

Gamma rays from the decay of an isomer in 190W116 have been observed following projectile fragmentation of a 1 GeV per nucleon 208Pb beam. An earlier experiment indicated decay from a (10-) isomer to the ground state rotational band. Improved statistics have enabled gamma coincidence and time-difference measurements to be made which alter the previous interpretation. Blocked BCS calculations have also been used together with reduced hindrance factors to indicate possible values of spin-parity for the isomer. [ABSTRACT FROM AUTHOR]

Using deformed Hartree-Fock and angular momentum projection (PHF) technique we try to understand the intrinsic structure and the systematics in the life times of K = 6+ isomers in the Hf isotopes (in 172-178Hf nuclei) and N = 104 Yb, Hf and W isotones. The band structure in 172Hf is reasonably well reproduced. The variation in the B(E2;2+ → 0+) values in the Hf isotopes as well as N = 104 isotones are well reproduced. The calculated K-forbidden E2 transition probabilities from the isomer bandheads to the 4+ yrast states qualitatively explain the variation of the lifetimes with N and Z. [ABSTRACT FROM AUTHOR]