Search

The role j15/2 neutron orbitals play in the transuranic region of actinides has been studied by exploring γ-ray transitions between yrast states in Np235, populated utilizing the nucleon-transfer reaction Np237(Sn116,Sn118). Two rotational sequences, presumably the two signatures of the ground-state band, have been delineated to high spin for the first time, with the α=+1/2 and α=-1/2 signature partners reaching 49/2 (tentatively 53/2+) and 47/2+ (tentatively 51/2+), respectively. Definite isotopic assignments for these in-band transitions were established through γ-ray cross correlations between Np235 and Sn118 and events where at least three γ rays corresponding to neptunium-like particles were detected. These transitions reveal clear upbends in the aligned angular momentum and kinematic moment of inertia plots; such a phenomenon could indicate a strong interaction between an aligned νj15/2 configuration crossing the ground-state band in Np235, which is based on a πi13/2 orbital. However, the lack of any signature splitting over the observed frequency range of the Np235 rotational sequences cannot remove the possibility of a πh9/2 assignment for the observed band. The role of the νj15/2 and πi13/2 alignment mechanisms in the deformed U-Pu region is discussed in light of the current spectroscopic data and in the context of the cranked-shell model.

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

Two high-spin regularly spaced rotational bands with large dynamical moments of inertia have been identified in 175Hf with the Gammasphere spectrometer. These new bands are very similar to the previously identified triaxial superdeformed bands in the hafnium nuclei. However, the new bands in 175Hf have been linked into the known level scheme and thereby provide the first firm spin assignments for these structures in this region. In order to understand the new bands, theoretical calculations have been performed based on the ULTIMATE CRANKER code. The new bands in 175Hf are deduced to be built upon highly deformed structures. No experimental evidence for triaxiality was established and this work suggests that the structure of the so-called "triaxial" superdeformed bands in the Hf nuclei may be quite different from those identified in the lighter mass Lu nuclei. Since the two highly deformed bands in 175Hf are associated with different deformations, this work also identifies the role of the intruder orbits in polarizing the nuclear shape.