A $T_{\frac{1}{2}}=18\mathrm{}$ ns isomer at $E_x=2986\mathrm{}$ keV has been found in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ and identified as the 19/$2^{+}$ member of the [$\left({}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}\right)5^{-}\otimes h_{\frac{9}{2}}\left(\mathrm{proton}\right)$] weak coupling multiplet. The $g$ factor of the state has been determined to be $g=0.368\mathrm{}\pm 0.008$. Multipole mixing ratios have been determined for three transitions connecting the $i_{\frac{13}{2}}$ single particle state in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ with states of the [$\left({}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}\right)3^{-}\otimes h_{\frac{9}{2}}\left(\mathrm{proton}\right)$] multiplet and with the ground state. In addition a 26%, 141 keV branch has been observed in the decay of the 15/$2^{+}$ member of the ($3^{-}\otimes h_{\frac{9}{2}}$) multiplet, resolving serious discrepancies between earlier Coulomb excitation work and theoretical expectations.

NUCLEAR REACTIONS ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}({}_{}{}^7{}_{}{}^{}\mathrm{Li},{}_{}{}^4{}_{}{}^{}\mathrm{He}2n\gamma$; measured $T_{\frac{1}{2}}$, $E_{\gamma }$, $g$, $\gamma -\gamma$ coin, Ge(Li) detectors; ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ deduced levels, $J$, $\pi$.

• Received 6 July 1977

DOI:https://doi.org/10.1103/PhysRevC.17.1359