Rayleigh scattering of neutron capture γ rays from U

Nineteen γ-ray lines in the energy range 0.4-3.0 MeV, produced by the Ni(n,γ) and Fe(n,γ) reactions, were scattered from a natural U target at angles of θ=1.02°for the Ni source, and θ=1.80°for the Fe source. Differential cross sections were measured relative to carbon and were found to be dominated completely by Rayleigh scattering. The smallness of the scattering angles and the large values of the Rayleigh cross sections present a unique opportunity to make an accurate comparison with the popular theoretical calculations based on the modified form factors. The results were found to agree fairly well with the form-factor calculations, but discrepancies averaging 8% were observed in the momentum transfer range 0.6-1.3 A-1.