Electric Dipole Transitions from the 2.6-MeV Septuplet inBi209

The resonant scattering of electron bremsstrahlung by the ${\frac{7}{2}}^{+}$, ${\frac{9}{2}}^{+}$, and ${\frac{11}{2}}^{+}$ members of the 2.6-MeV septuplet in ${\mathrm{Bi}}^{209}$ has been studied. On the basis of the scattered intensities, and assuming ground-state branching ratios $\frac{{\Gamma }_0}{\Gamma }$ of 0.5, 1.0, and 1.0, respectively, ground-state transition widths of ${\Gamma }_0(2.581, {\frac{7}{2}}^{+})<\mathrm{}10\mathrm{}$ meV, ${\Gamma }_0(2.563, {\frac{9}{2}}^{+})=30\mathrm{}\pm 5$ meV, and ${\Gamma }_0(2.598, {\frac{11}{2}}^{+})=9.0\mathrm{}\pm 2.4$ meV were obtained. The observed transition strengths agree well with the predictions of the particle-vibration model in the form used by Hamamoto, with ${e_{\mathrm{eff}}}^2\mathrm{}\left(E1\mathrm{}\right)=0.05\mathrm{}$.