SUPERDEFORMED TRIAXIAL BANDS IN LU-163,LU-165

An experimental investigation of the nucleus Lu-165, using the reactio ns Ba-138(P-31,4n)Lu-165 and Sm-150(F-19,4n)Lu-165 at beam energies of E = 155 and 95 MeV, respectively, has been performed. Among other add itions to the existing level scheme, a new band, with transition energ ies almost identical to a strongly deformed (beta(2) similar to 0.42) pi(13/2) [E660 1/2(+)] band recently discovered in Lu-163 has been est ablished. A theoretical analysis of the structure of the two Lu isotop es, Lu-165 and Lu-163 is carried out by detailed calculations of total potential energy surfaces for specific configurations, By a diabatic treatment of crossings specific proton configurations as pi(13/2) [660 1/2(+)] are identified throughout the deformation space and as a func tion of spin. It is found as a general feature that well deformed loca l minima of considerable nonaxial symmetry coexist with a normal defor med global minimum. The depth of these local minima depend on configur ation, The structure of the different global and local minima found in these surfaces are analysed and discussed in terms of occupation of a vailable basis configurations and their orientation relative to the ro tation axis. The strongly deformed minima are found to belong to a gro up of superdeformed triaxial structures, expected to appear at low ene rgies for certain favourable combinations of proton and neutron number s.