Thermal-neutron capture by 208Pb

J. C. Blackmon, ORNL Physics Division
S. Raman, ORNL Physics Division
J. K. Dickens, Joint Institute for Heavy Ion Research
R. M. Lindstrom, Analytical Chemistry Division
R. L. Paul, Analytical Chemistry Division
J. E. Lynn, Los Alamos National Laboratory


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.