Anomalies in the α-Decay Energies and Half-Lives of Neutron-Deficient Po Isotopes

The transition rates of ΔL=0 - transitions in the lightest Po isotopes are considerably slower than the transition rates of the heavier ones, even leading to a considerable deviation in the classical Geiger-Nuttall plot. Evidence will be given that due to particle-hole excitations through the Z=82 proton shell, the groundstate of the lighter Po isotopes becomes deformed and direct - decay to the spherical groundstate of the corresponding Pb isotopes is highly retarded.