High-spin state spectroscopy of Dy-143 - art. no. 064301

The Dy-143 nucleus has been studied with the Mo-92 (Fe-54, 2pn gamma) react ion at 240 MeV incident energy. A rich variety of structures was observed a t high spin. The nearly spherical nuh(11/2) = 11/2 isomer is the basis of a negative parity irregular yrast structure which is observed up to I=51/2. A positive parity band presenting a large dynamic moment of inertia was obs erved, similar to the deformation enhanced nui(13/2) bands known to exist i n this mass region. However, we propose an alternative assignment for this band, namely the triaxial collective minimum with beta =0.2 predicted by to tal Routhian surface calculations for a N-osc=4 quasineutron excitation cou pled to pairs of aligned quasiparticles. Another negative parity structure, with strong M1 and weak E2 crossover transitions, was observed.