ROTATIONAL BANDS IN THE DOUBLY ODD PM-138

The band structures of the doubly-odd Pm-138 nucleus have been investi gated using the In-115(Si-28, 2p3n)Pm-138 reaction at a beam energy of 145 MeV. The three previously known rotational bands viz., (i) the yr ast one based on the pi h(11/2) x nu h(11/2) configuration, (ii) a Del ta I = 2 band with pi h(11/2) x nu[400]1/2(+) configuration at lower f requency but with a change in the neutron configuration to nu[660]1/2( +) at higher frequency, and (iii) one consisting of stretched E2 casca des at lower frequency but of dipole transitions after backbend and wi th suggested configuration of pi[413]5/2(+) x nu h(11/2) have been mod ified and extended to higher spins. Two new bands have been identified . Of these, one consists of only quadrupole transitions, similar to th at observed in band (iii), mentioned above, while the other consists o f dipole transitions. The observed level properties have been compared to theoretical calculations performed within the Particle Rotor Model (PRM) with axial core and cranked shell model. The experimental branc hing ratios and B(M1)/B(E2) ratios of the transitions in the yrast ban d are well reproduced by PRM, assuming an axial prolate core. (C) 1998 Elsevier Science B.V.