Fine structure in the alpha decay of even-even nuclei as an experimental proof for the stability of theZ=82 magic shell at the very neutron-deficient side

Fine structure has been observed in the {α} decay of ²⁰²Rn, 194,196,198Po, 186,188Pb, and 180,182,184Hg and has led to the identification of low-lying 0⁺ states in ¹⁹⁸Po, 190,192,194Pb, 182,184Hg, and 176,178,180Pt. The large variation in the hindrance factors of the {α} decay to the exicted 0⁺ state is a proof for the persistence of the Z=82 shell closure at the neutron-deficient side. Comparing the reduced widths of the {α} decays to the ground and excited states offers a unique way to probe the proton particle-hole character of the 0⁺ states in this region.