Medium-spin states in the N=80 nuclei 139Pr and 141Pm

The level structures of 139Pr and 141Pm have been investigated using (p,2n), (3He,3n) and (α,4n) reactions and methods of in-beam γ-ray and electron spectroscopy. Fourteen new levels with spins up to (23+/2) were observed in 139Pr and seventeen new levels with spins up to 19-/2 in 141Pm. The level structures in both nuclei can be described by coupling the odd-proton intrinsic states to the excitations of the doubly even core. The ordering of the levels in the πhsub(11/2)x2+ multiplet is discussed on the basis of the triaxial rotor-plus-particle model calculations. The calculations suggest that a transition from a basically prolate to an oblate triaxial shape takes place between the neutron numbers N = 78 and N = 80. A γ deformation of 34 was deduced for both 139Pr and 141Pm. (author)