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High-spin states in Hf168 were populated in the Zr96(Ge76,4n) reaction and the decay γ rays measured with the Gammasphere spectrometer array. Previously known bands were extended to significantly higher spins and seven new bands were established. The results were interpreted within the framework of the cranked shell model with the help of comparisons with neighboring nuclei. The observation of full alignment in band crossings at a rotational frequency ω~0.55 MeV revealed that these crossings are associated with proton alignments involving h11/2 and h9/2 orbitals. The characteristics of one strongly coupled high-K band indicate that the deformation-aligned configuration is built on the same six quasiparticles that constitute the high-spin structure of a rotationally aligned band. This leads to the coexistence of two coupling schemes, deformation and rotation alignment, in six-quasiparticle structures involving the same orbitals.

Possible decay pathways associated with three candidates for triaxial strongly deformed (TSD) bands in Hf168 have been investigated. The spin and excitation energy of the strongest band, TSD1, were determined approximately based on γ-ray coincidence relationships. Discrete links were established for the second band. The overall agreement between the observed properties of the bands and cranking calculations using the ULTIMATE CRANKER code provides strong support for an interpretation where band TSD1 is associated with a TSD minimum, (2,γ)~(0.43,20°), involving the π(i13/2)2 and the ν(j15/2) high-j orbitals. This constitutes the first identification of a TSD band in Hf isotopes, which has been long-predicted by theoretical studies. The second band is understood as being associated with a near-prolate shape and a deformation enhanced with respect to the normal deformed bands. It is proposed to be built on the π(i13/2h9/2)ν(i13/2)2 configuration.

Multiple band structures in 179Au are established from γ-ray spectroscopic measurements with Gammasphere at the Argonne Fragment Mass Analyzer. The yrast band, based on the 13/2+ proton, confirms the predicted drop in excitation energy of the prolate deformed band head as compared to the heavier isotopes. The implications for the prolate energy minimum in odd-mass Au nuclei beyond the neutron i13/2 midshell (N

High-spin states in 154Dy were studied with the Gammasphere spectrometer using the 36S(122Sn,4n) reaction. Band terminating states were identified in the spin range I= (36-48)ℏ, and were found to compete with collective rotational cascades up to the highest observed spins. Several "sidebands" feeding the terminating structures were identified as well. A band dominated by M1 transitions was observed to terminate at Iπ = 42-. The data are interpreted within the framework of configuration-dependent cranked Nilsson-Strutinsky calculations without pairing.

Spectra of the E2 quasicontinuum γ rays feeding different spin regions of the 154Dy yrast line have been extracted. These are compared with corresponding theoretical spectra obtained by numerical simulations based on temperature-dependent Hartree-Fock theory, with thermal shape fluctuations. In this manner, different regions of the spin-energy plane can be examined. The results support the predictions of a smeared-out phase transition at high spin above the yrast line.

The highest-spin discrete states (I ∼ 60 ℏ and Ex ∼ 30 MeV) in normal deformed nuclei have been observed in the rare-earth isotope 156Dy using the 124Sn(36S,4n) reaction in conjunction with the GAMMASPHERE spectrometer. The positive parity yrast sequence appears to evolve smoothly from a prolate (collective) towards an oblate (non-collective) shape, in contrast to the sudden shape change observed in the isotone 158Er. Terminating states are identified in the negative parity sequences at Iπ = 52- and 53- and specific multi-particle-hole configurations are assigned by comparison with cranked Nilsson-Strutinsky calculations. An order of magnitude increase in the interaction strength between close lying high-spin weakly collective structures is determined compared with that found in the lower-spin strongly collective domain. These results give valuable insight into the interplay between collective and terminating structures, and their competition for yrast status in the 40 - 60 ℏ spin range.

In-beam γ-ray transitions in 181Hg, the lightest odd-A Hg isotope known thus far, have been identified from fragment mass-γ and γ-γ coincidence measurements. Five prolate deformed rotational bands were placed in the level scheme. A decoupled band built on the strongly prolate deformed 1/2-[521] ground state was observed up to 29/2-. A 5/2-[512] configuration is suggested for a pair of strongly coupled bands displaying no signature splitting. The other two bands are also signature partner bands. They are populated with the largest intensity and exhibit splitting. They have been associated with the mixed neutron i13/2 orbitals and are proposed to decay to an i13/2 isomeric state associated with an oblate state.

A superdeformed band of 15 transitions has been found in the 155Dy nucleus. The measurement was performed with a backed target and the large deformation was inferred from the measured Doppler shifts. The new band displays an intensity pattern much different from typical superdeformed bands in this mass region. The dynamic moment of inertia is essentially identical to that of band 1 in 153Dy and is somewhat larger than those of the yrast superdeformed bands in 152, 154Dy, suggesting that the associated configuration has an additional N = 7, j15/2 intruder orbital occupied with respect to the 154Dy core.