HIGH-SPIN STRUCTURE OF Y-84

The high spin levels of Y-84 have been established up to 12 MeV excita tion energy and probable spin of 25(+) through the reaction Co-59(Si-2 8, 2pn)Y-84 using in-beam gamma-ray spectroscopic techniques. The gamm a transitions in Y-84 have been identified through the particle-gamma coincidences. The level scheme was constructed through the gamma-gamma coincidences, angular distribution, and directional correlation orien tation ratios. The positive parity yrast band built on the (pi g(9/2) circle times nu g(9/2)) configuration shows a large signature splittin g and a signature inversion at I similar to 11 ($) over bar h. The mea sured B(E2; I --> I - 2) values give a deformation beta(2) similar to 0.17. The negative parity band shows a signature inversion at I simila r to 11 ($) over bar h and B(M1; I --> I-1) enhancement for I > 11 ($) over bar h. The projected Hartree-Fock and the cranked shell model ca lculations provide an understanding for the observed properties of the energy levels in Y-84.