Gamma-ray Lines from (n,2n) and (n,n') Reactions in Radiogenic and Natural Lead

Discrete γ-ray lines emitted after (n,2n) and (n,n') reactions in radiogenic and natural lead at 15.5 MeV neutron energy have been studied. Differential 120° cross sections have been determined relative to the cross section for the ground state transition from the 4.44 MeV level of 12 C populated through inelastic scattering. The (n,2n) and (n,n') contributions to the cross sections for the most dominant γ-ray lines in 206 Pb and 207 Pb have been separated. Upper and lower limits of the cross sections for (n,2n) and (n,n') reactions in lead are estimated. The results indicate that the statistical theory of nuclear reactions fails to give a correct description of neutron emission processes in lead at 15 MeV neutron energy.