High spin behavior of 83Y from GAMMASPHERE

Nuclei in the A ∼80 region exhibit many interesting features of nuclear structure, including varying degrees of deformation and band termination. Changes in collectivity, either through shape changes, or exhaustion of the shell model space, is of particular interest. Shape polarization, driven by the occupation of key intruder orbitals, is manifest at both low and high spins 83Y lies at the center of this region and its shape and structural properties at all spins is of interest. We have investigated high spins in 83Y using the reaction 58Ni(29Si, 3pn) at 110 MeV and the GAMMASPHERE array with 36 Compton-suppressed HP-Ge detectors. Both thin and thick targets were used for the observation of weak transitions and the measurement of DSAM lifetimes. Some eighteen new transitions were observed with a highest observed probable spin state of (53/2). At the top of the π = +(-), α = +1/2(-1/2) sequences, the bands fork into two different structures. A possible third band-crossing, at a probable spin state of (47/2+) and characterized by a sharp backbend, is observed, just above the highest previously known transition in this band. Results will be discussed in terms of the CSM