The $\gamma$ decay of excited states in ${}_{}{}^{210}{}_{}{}^{}\mathrm{Bi}$ up to 3250-keV excitation energy has been studied with the ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}(d, p\gamma )$ reaction at 8.0- and 10.0-MeV incident deuteron energies, using particle-$\gamma$ and $\gamma -\gamma$ coincidence techniques and a pulsed deuteron beam. For almost all of the states excited in this reaction, $\gamma$-decay branching ratios were obtained. The branched decay of states with a dominant configuration ($d_{\frac{5}{2}}^{\nu }\otimes h_{\frac{9}{2}}^{\pi }$) into states with a ($g_{\frac{9}{2}}^{\nu }\otimes h_{\frac{9}{2}}^{\pi }$) configuration was analyzed to determine experimentally the amount of configuration mixing between these two multiplets. The obtained mixing amplitudes are in remarkably good agreement with shellmodel calculations. From the observed lifetimes of the ${(g_{\frac{9}{2}}^{\nu }\otimes h_{\frac{9}{2}}^{\pi })}_{5^{-},7^{-}}$ states, a reduced matrix element of $〈g_{\frac{9}{2}}^{\nu }\parallel E2\mathrm{}\parallel g_{\frac{9}{2}}^{\nu }〉=-38\mathrm{}\pm 4 e$ ${\mathrm{fm}}^2$ has been extracted. This value is in good agreement with an intermediate coupling calculation which yields $-35\mathrm{} e$ ${\mathrm{fm}}^2$.

• Received 9 August 1972

DOI:https://doi.org/10.1103/PhysRevC.7.2137