Reinvestigation of the collective band structures in odd-odd 138 Pm nucleus

The high-spin states in the odd-odd 138 Pm nucleus have been reinvestigated via the 124 Te( 19 F, 5 n ) reaction at the beam energy of 103 MeV. Most of the known transitions and levels are confirmed. A number of bands are revised and one new band has been established. For the yrast πh 11/2 ⊗ νh 11/2 band based on 8 + state, no evidence supporting the occurence of signature inversion is found. The experimental and theoretical B ( M 1)/ B ( E 2) ratios have been calculated for band (2), which support the πg 7/2 [413]5/2 + ⊗ νh 11/2 [514]9/2 − Nilsson configuration assignment. Four bands with ΔI = 2 transitions are tentatively assigned as doubly decoupled bands. The other three bands are proposed as oblate-triaxial bands. The possible configuration assignments for these bands are also discussed under the calculations of total Routhian surface and particle-rotor model.