Study of Gamma Radiation from Interaction of 14.7-MeV Neutrons with ²⁰⁸Pb

The gamma radiation from the interaction of 14.7-MeV neutrons with ²⁰⁸Pb is investigated by high-resolution germanium-detector gamma-ray spectroscopy by using an enriched ²⁰⁸Pb sample. Cross sections for 14 gamma-ray lines from the ²⁰⁸Pb(n,n′γ) and ²⁰⁸Pb(n,2nγ) reactions are measured at an emission angle of 124 deg. The results are compared with measurements from previous studies and with predictions based on the statistical theory of nuclear reactions (including direct and precompound contributions). The current results, especially for the ²⁰⁸Pb(n,n′γ) reaction, are considerably smaller than the results of most of the measurements of the previous studies probably because of the neglect of important sources of background, e.g., gamma-ray production in lead shielding, in the previous studies. Agreement with theory is adequate for the strong transitions between the lowest levels in ²⁰⁷Pb and ²⁰⁸Pb, but large discrepancies exist for the weaker transitions, especially for gamma-ray transitions from levels where experimental knowledge of branching ratios is missing.