HIGH-LYING 3-QUASI-PARTICLE BANDS AND SIGNATURE SPLITTING IN RB-81

Two new high-lying level sequences of negative parity have been identi fied in the odd-proton nucleus Rb-81 by in-beam gamma-ray spectroscopy using the reactions Br-79(alpha, 2n) at 27 MeV and Zn-68(F-19, alpha2 n) at 72 MeV. One sequence, dominated by M1 transitions, is interprete d as a three-quasiparticle band predominantly containing a neutron in the p1/2, p3/2, or f5/2 subshell coupled to g9/2 proton and g9/2 neutr on excitations. The other new level sequence forms the three-quasipart icle extension of the unfavored negative-parity band, but the states d ecay also by E1 transitions. The signature splitting points to a confi guration where an aligned g9/2 proton pair is involved.