Quadrupole and octupole collectivity in light Po isotopes

The level structure of 196Po has been studied using a 160Dy (40Ar, 4n) reaction and a recoil-catcher technique to reduce fission. The results showed a sharp drop off in the first (2+) and (4+) energies relative to systematics implying an abrupt increase in the quadrupole collectivity at N=112. In addition, second (2+) and (4+) states were identified at 859 and 1388 keV, respectively, suggesting the discovery of a 4p2h deformed band in Po isotopes which is related to known 2p2h proton bands in several Pb isotopes. A prompt 183W(20Ne, 5n) experiment located similar scond 2+ and 4+ states at 1039 and 1483 keV in 198Po providing corroboration and extended information of the properties of the new Po deformed bands. A measured halflife of 850(90) ns for the 2491 keV (11-) state in 196Po implied collective E3 contributions to the extracted B(E3; 11-→8+)=27(5) W.u. (orig.)