The photon spectrum from stopped ${\pi }^{-}$ absorption on ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ was measured in the 50-150 MeV region with a high-resolution pair spectrometer. The total radiative branching ratio is 0.98 ± 0.10%. Transitions to the single-particle states of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$ are weak, in agreement with calculations presented. Considerable transition strength is observed to states of ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$ at 6-16 MeV excitation with evidence for a narrow peak at 7.9 ± 0.4 MeV. Present evidence favors the interpretation of this peak as excitation of the analog of a $T_{>}$ giant quadrupole resonance expected at ≃26 MeV in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$.

NUCLEAR REACTIONS ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}({\pi }^{-},\gamma )$ with stopped ${\pi }^{-}$; measured photon spectrum (50-150 MeV) and radiative branching ratio using pair spectrometer of 2 MeV resolution. Shell model calculations compared with measurements.

• Received 8 April 1974

DOI:https://doi.org/10.1103/PhysRevC.10.1140