Widths for s- and d-wave α-decay of neutron-deficient isotopes with Z 82

The α-decay of the nucleides ^188–192Pb, ¹⁸⁰Hg, and ¹⁷⁶Pt has been studied after on line mass separation of spallation products from reactions with 600 MeV protons. For the lead isotopes, the K X-ray/α ratios were determined, and from these partial α half-lives were deduced. In the decay of 6 sec ¹⁷⁶Pt, a 1.4% α-branch was found to the 228 keV 2⁺ level of ¹⁷²Os, while for ¹⁸⁰Hg an upper limit of 10⁻³ (relative to the ground-state α-branch) could be put on the intensity of an assumed rotational fine-structure component. The systematics of reduced s-wave (0⁺ → 0⁺) α-widths is discussed. The lead isotopes show a surprising trend: the reduced s-widths vary from a very small value for ¹⁸⁶Pb (deduced from the heavy-ion cross sections of Gauvin et al.) to a quite large value for ¹⁹²Pb. The systematics of d-wave (0⁺ → 2⁺) hindrance factors (relative to the ground-state branch) shows that these range from 1 to 4 for the actinides, while for platinum and mercury one finds 8 and ≈ 50, respectively.