Observation of a doublet band in the nucleus 128 Pr

The doubly odd nucleus ${}^{128}\\mathrm{Pr}$ was studied via in-beam \\ensuremath{\\gamma}-ray spectroscopy using the ${}^{40}\\mathrm{Ca}{+}^{92}\\mathrm{Mo}$ reaction at 190 MeV. Five rotational bands were observed and assigned to configurations involving proton and neutron orbitals close to the Fermi level. The observed bands are discussed in the framework of the three-dimensional (3D) tilted axis cranking (TAC) model. Two of the negative-parity bands have almost degenerate energy levels, which suggests an interpretation in terms of the pseudospin doublet $[32\\ifmmode \\tilde{}\\else \\~{}\\fi{}1].$ It was impossible, however, to reproduce the observed small level spacing by either 3D TAC or two-quasiparticle--rotor model calculations.