A novel manifestation of alpha clustering in (212)Po: Pure alpha-(208)Pb states revealed by their enhanced E1 decays
Abstract
Excited states in (212)Po have been populated by a transfer using the (208)Pb((18)O,(14)C) reaction and studied with the Euroball gamma multidetector array. The level scheme of (212)Po has been extended up to similar to 3.2 MeV excitation energy. Spin and parity values have been assigned thanks to the measurements of gamma angular distributions and gamma-gamma angular correlations. Several gamma lines have been found to be shifted by the Doppler effect, allowing for the measurements of the associated lifetimes by the DSAM method. The values, found in the [0.1-1.4] ps range, lead to very enhanced E1 transitions. The emitting states, which have non-natural parity values, are the fingerprints of the "alpha-(208)Pb" structure present in (212)Po. They are in the same excitation-energy range as the states issued from shell-model configurations.