SHAPE TRANSITION IN ODD-ODD A-APPROXIMATE-TO-130 NUCLEI

A systematic analysis of rotational bands in doubly odd nuclei in the mass region A = 130-140 is carried out using a shell model configuration mixing approach. The shell model (many-body) basis is constructed by projecting out deformed quasiparticle (Nilsson + BCS) states onto good angular momenta. The hamiltonian is assumed to be a sum of (spherical) single-particle hamiltonian and a schematic two-body interaction, which consists of Q . Q + (monopole) pairing + quadrupole-pairing forces. The analysis indicates a shape transition from prolate (N = 73) to oblate (N = 79) shape as a function of neutron number. Agreement between theoretical results and experimental data is quite satisfactory except for gamma-deformed nuclei (N = 75 and 77).