Resonant photon scattering from ${}_{}{}^{206,207,208}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ has been measured from 4 MeV to the neutron thresholds using enriched targets, Ge(Li) detectors and bremsstrahlung beams with end-point energies of 7.0, 7.5, 7.6, 8.0, 8.5, and 10.4 MeV. Energies and values of $\frac{g{{\Gamma }_0}^2}{\Gamma }$ were obtained for many levels not observed in previous photon experiments. Spins of levels in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ were determined from the angular distributions, and ground-state branching ratios were obtained from self-absorption measurements for seven transitions in ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$. The results are compared with earlier spectroscopic studies and with lower resolution average cross-section measurements. The spectra of ${}_{}{}^{207}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}$ are discussed in terms of the excitations of the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ core.

NUCLEAR REACTIONS ${}_{}{}^{206,207,208}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{209}{}_{}{}^{}\mathrm{Bi}(\gamma , \gamma )$; enriched targets; resonance fluorescence with 7.0, 7.5, 7.6, 8.0, 8.5, and 10.4 MeV bremsstrahlung. Measured $E_{\gamma }$, $I_{\gamma }$ at 90° and 127°, and self-absorption; deduced $\frac{g{{\Gamma }_0}^2}{\Gamma }$, $\frac{{\Gamma }_0}{\Gamma }$, $J$.

• Received 24 March 1980

DOI:https://doi.org/10.1103/PhysRevC.22.1420