The production of gamma-rays by neutrons

The production of γ-radiation due to the passage of neutrons through matter was discovered by Lea (1935) and has been subsequently investigated by a number of workers. The experiments of Lea with fast neutrons appeared to indicate that the γ-radiation arises from a process of inelastic scattering of neutrons. Evidence for the occurrence of inelastic scattering of fast neutrons has been obtained by Danysz and others (1934) and Ehrenberg (1935) and it has been pointed out by Bohr that on current theories of the interaction between fast neutrons and atomic nuclei most of the scattering would be expected to be inelastic. On the other hand, measurements of the absorption of slow neutrons in elements which emit γ-rays (e. g. Cd, Hg) show that the absorption is a sharp resonance process, and it is assumed that the γ-radiation in these cases arises from neutron capture. The present work was undertaken with a view to determining the energies of the neutrons which give rise to the γ-radiation, in an attempt to throw some light on the mechanism of its production.