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

The high-spin states in the odd-odd ¹³⁸Pm nucleus have been reinvestigated via the ¹²⁴Te(¹⁹F, 5n) 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 x νh_11/2 band based on 8⁺ state, no evidence supporting the occurence of signature inversion is found. The experimental and theoretical B(M1)/B(E2) ratios have been calculated for band (2), which support the πg_7/2[413]5/2⁺ x 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. (orig.)