High-spin studies of172,173Os: Complex alignment mechanism

High-spin states of ${}_{}{}^{172}{}_{}{}^{}\mathrm{Os}$ have been investigated by γ-γ coincidence studies. These states were populated by the ${}_{}{}^{144}{}_{}{}^{}\mathrm{Nd}$ ${(}^{32}$S,4n) reaction using 162-MeV ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ ions. Gamma-gamma coincidence measurements were made with a Compton-suppression spectrometer system. The yrast band was observed up through the ${30}^{+}$ state, and four sidebands were deduced from γ-γ coincidence relationships. A band identified as belonging to ${}_{}{}^{173}{}_{}{}^{}\mathrm{Os}$ was also observed. Results were interpreted using average nuclear field calculations which incorporated the deformed Woods-Saxon potential with its ‘‘universal’’ parametrization, a cranking approximation, and the Hartree-Fock-Bogoliubov method. The calculations indicate the presence of strongly interacting quasiparticle band crossings for 0.2<ħω<0.3, in semiquantitative agreement with experiment. Both the quasiparticle band structures and decline of neutron pairing are discussed.