Interpretation of the high spin states in Lu-161: A paired and unpaired study

A paired cranked Nilsson-Strutinsky-Bogoliubov (CNSB) model is presented, which employs the same method to calculate the liquid-drop energy and moment of inertia as the unpaired cranked Nilsson-Strutinsky (CNS) model. In the CNSB model, the energy minimization is carried out in the mesh of pairing gaps Delta and Fermi levels lambda as well as deformation parameters. The high spin states in Lu-161 are then investigated with the CNSB and CNS models. The terminating structure shows a striking similarity with these two models. Combining the CNSB and CNS models, a complete understanding of high spin structures, including the normal deformed (ND) and triaxial strongly deformed (TSD) bands and observed side bands in Lu-161, is achieved. It appears that the only important paired crossings are the first i(13/2) neutron crossing and the first h(11/2) proton crossing. For the description of the unpaired high spin crossings, it is important to be able to distinguish between the pseudospin partners in the proton N = 4 shell, (d(5/2), g(7/2)) and (d(3/2), s(1/2)). The yrast bands are predicted to terminate, which explains the structure of a TSD-like band X2. A band crossing at I approximate to 36.5 for the TSD band in Lu-161, unique within the chain of even-N Lu isotopes, is well described by the CNSB model