FINE STRUCTURE IN THE ALPHA-DECAY OF THE NEUTRON-DEFICIENT ~(191)Po AND ~(191)Bi ISOTOPES

摘要

The α-decay properties of the neutron-deficient ~(191)Po and ~(191)Bi nuclei have been investigated at the RITU gas-filled separator using the 5n and p4n evaporation channels of the ~(36)Ar+~(160)Dy→~(196)Po* reaction. In contrast to previous studies two α-decaying isomeric states were observed in the decay of ~(191)Po. Evidence was found for α-decay to excited levels in the ~(187)Pb daughter nucleus. The tentative interpretation of these levels could be a weak coupling of the odd neutron to an intruder 2p-2h deformed 0+state in the even-even core. The difference in the reduced α widths of the α transitions towards the ground state and excited state points to a deformed 13/2+ isomeric state in ~(191)Po. Branching ratios of b_a(~187m)Pb=12(2)％ and b_a(~187g)Pb=7(2)％ have been experimentally measured. For ~(191)Bi two new alpha-lines have been observed. A more precise half-life value of T_(1/2)=115(10)ms vaw determined for ~(191m)Bi.