Remarks on Some Questions of Neutron Optics

Abstract

Several derivations of the expression for the index of refraction of neutrons are discussed and difficulties recently raised are cleared up. The theory is extended to cover cases involving absorption (through capture or incoherent scattering). Formulas for the scattering due to disorder in crystals are used for the determination of scattering amplitudes of isotopes in agreement with direct experiments. It is shown how the polarization of neutrons scattered under small angles can be used to obtain information about the structure of mixed crystals. The problem of primary and secondary neutron extinction is also discussed in the light of a recent publication.