Thermal-neutron capture by ${}^{208}\mathrm{Pb}$

We have observed seven γ rays following subthermal-neutron capture by ${}^{208}\mathrm{Pb}$ and incorporated them into a level scheme of ${}^{209}\mathrm{Pb}$ consisting of five excited levels. The measured neutron separation energy of ${}^{209}\mathrm{Pb}$ is 3938.0±0.5 keV. The thermal-neutron capture cross section of ${}^{208}\mathrm{Pb}$ was determined to be 230±12 μb. The theoretical estimates are 860 μb or 550 μb, depending on the model used for the compound-nuclear component; however, these values are not inconsistent with the data if the statistical distribution of the theoretical estimates is taken into account. The thermal-neutron capture cross sections for ${}^{206}\mathrm{Pb}$ and ${}^{207}\mathrm{Pb}$ were also determined and found to be 26.6±1.2 mb and 610±30 mb, respectively.