Oblate collectivity in sup 197,198 Pb

Evidence for collective behavior in the high-spin region of neutron deficient lead nuclei is provided by the observation of four collective structures in {sup 197,198}Pb. These bands consist of strong dipole (M1) transitions with a few E2 crossover transitions observed. The transition energies of three of these bands show a rather regular behavior while those of one of them show an irregular behavior. We interpret the regular bands as oblate collective bands built on oblate proton and neutron states, whereas the irregular band might either be built on a state with very small oblate deformation, or be a triaxial rotational band. A lifetime measurement (DSAM) has been done for the regular bands in {sup 198}Pb. Neutron and proton configurations for the bands are suggested from the results of quasi particle Routhians and total Routhian surface (TRS) calculations.