6533b855fe1ef96bd12b1a89

RESEARCH PRODUCT

Hindered (Δl=0) Alpha Decay and Shape Staggering in191Po

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Two $\ensuremath{\alpha}$-decaying isomeric states were observed in ${}^{191}\mathrm{Po}$ with ${E}_{\ensuremath{\alpha}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}7334(10)\mathrm{keV}$ and $\mathrm{T}{}_{1/2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}22(1)\mathrm{ms}$ for ${}^{191g}\mathrm{Po}$ and $\mathrm{E}{}_{\ensuremath{\alpha}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}7378(10)\mathrm{keV}$ and $\mathrm{T}{}_{1/2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}98(8)\mathrm{ms}$ for ${}^{191m}\mathrm{Po}$. Evidence was found for fine-structure decay to excited levels in the ${}^{187}\mathrm{Pb}$ daughter nucleus. The tentative interpretation of these new levels involves the weak coupling of the odd neutron to an intruder $\ensuremath{\pi}(2p\ensuremath{-}2h)$ deformed ${0}^{+}$ state in the even-even core. The long half-life of the ${}^{191m}\mathrm{Po}$ $(\ensuremath{\Delta}l\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0)$ $\ensuremath{\alpha}$ decay points to a deformed ${13/2}^{+}$ isomeric state in ${}^{191}\mathrm{Po}$.