Close doublet structures in ¹⁰³Mo, ^{109, 111}Ru, and neighbours: Rotation-alignment for the half-filled h11/2 subshell?

Several new γ transitions are assigned to 103Mo and 109, 111Ru in a γ-γ-γ coincidence study from the spontaneous fission of 252Cf with 72 Compton suppressed Ge detectors in Gammasphere. A close doublet structure of an odd-parity band except near its bandhead is a common feature not only of the nuclei studied here but of many others with 61 ≤ N ≤ 67. This doublet structure may be a general consequence of rotation alignment for configurations of half-filled j-shells, which are only weakly coupled to the deformed shapes.