High-spin states and collective band structures in the odd–odd ¹⁴⁰Pm nucleus

The high-spin states of ¹⁴⁰Pm have been investigated through the reaction ¹²⁶Te(¹⁹F, 5n) at a beam energy of 90 MeV. A previous level scheme based on the 8⁻ isomer has been updated with spin up to 23 ℏ. A total of 22 new levels and 41 new transitions were identified. Six collective bands were observed. Five of them were expanded or re-constructed, and one of them was newly identified. The systematic signature splitting and inversion of the yrast πh_11/2⊗νh_11/2 band in Pr and Pm odd–odd isotopes has been discussed. Based on the systematic comparison, two ΔI = 2 bands were proposed as double-decoupled bands; other two bands with strong ΔI = 1 M1 transitions inside the bands were suggested as oblate bands with γ ∼ −60°; another band with large signature splitting has been proposed with oblate-triaxial deformation with γ ∼ −90°. The characteristics for these bands have been discussed.