RECOIL DISTANCE LIFETIME MEASUREMENTS OF STATES IN THE OBLATE DIPOLE BANDS OF PB-197,PB-198

Lifetimes of states in four of the oblate dipole bands in Pb-197, Pb-1 98 have been measured with the recoil distance technique. Using all th e available data on lifetimes and branching ratios, and assuming pure magnetic dipole transitions, we deduce reduced transition probabilitie s. The results are consistent with weakly oblate collective structures involving high-K proton configurations coupled to rotationally aligne d neutrons. Comparisons are made to the theoretical estimates of the D onau and Frauendorf semi-classical model and the tilted axis cranking (TAC) model.