BAND CROSSINGS IN Y-83 REVISITED

Gamma rays from the reaction Si-28(Ni-58, 3p)83Y at a beam energy of 195 MeV were recorded in recoil-gamma- and gamma-gamma-coincidence mode with the POLYTESSA array and the Daresbury recoil mass separator. The known rotational bands were extended up to probable spins 49/2+ and 45/2-; many new interconnecting dipole transitions and an additional cascade were established. The bands are interpreted in terms of the cranked shell model; they exhibit two band crossings each, associated with g9/2 neutron and proton alignment. In the negative-parity yrast bands a strong signature inversion with DELTA-e' = -100 keV and a crossing pattern alternating in the favoured and unfavoured band develop. Hartree-Fock-Bogolyubov cranking calculations with a Woods-Saxon single-particle potential have been performed to illustrate the various shape changes and explain this signature inversion.