Thermal-neutron capture by 208Pb
We have observed seven γ rays following subthermal-neutron capture by 208Pb and incorporated them into a level scheme of 209Pb consisting of five excited levels. The measured neutron separation energy of 209Pb is 3938.0±0.5 keV. The thermal-neutron capture cross section of 208Pb 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 206Pb and 208Pb were also determined and found to be 26.6±1.2 mb and 610±30 mb, respectively.