Weak coupling and dipole bands in [Formula Presented]

Excited states in the nucleus [Formula Presented] have been investigated by in-beam γ-ray spectroscopic techniques using the Gammasphere array. The reaction [Formula Presented] at a beam energy of 134.5 MeV was used to populate states of [Formula Presented] The level scheme of [Formula Presented] has been extended up to 5.1 MeV excitation energy and spin [Formula Presented] The lower part (below [Formula Presented]) presents the general features common in all odd-mass Pb isotopes, i.e., spherical states built on the [Formula Presented] isomer, with bandlike structures that follow weak-coupling expectations. In the upper part of the level scheme two dipole bands are observed with bandhead energies of [Formula Presented] and 2.291 MeV. A comparison of dipole band 1 with the strongest negative-parity dipole bands in the heavier odd-mass Pb isotopes reveals striking similarities. The spherical states are interpreted as the coupling of the [Formula Presented] neutron hole to the yrast states in the even-mass [Formula Presented] core. The dipole bands are interpreted as [Formula Presented] cascades which arise from the coupling of two protons in high-[Formula Presented] orbitals above the [Formula Presented] gap to neutron holes in the [Formula Presented] orbital.