Interference between Rayleigh and nuclear resonant scattering in crystals

Abstract

The recoil-less resonant scattering of y-rays by nuclei in a crystal will show diffraction effects. The crystal will in general scatter incident radiation by both nuclear (Mössbauer) and electronic (Rayleigh) processes and the effects due to interference between these two are of interest because they can give information about the phase of the Rayleigh scattering. In this paper, the theory developed by Moon (1961) for this interference has been derived in a different form so that allowance can be made for the effect of the energy dependence of the absorption near resonance. The various factors influencing the size of the interference effect for diffraction in pure iron of 57 Fe y-rays are discussed. General confirmation of the theory has been obtained from experimental measurements of the scattering from natural and isotopically enriched iron specimens. Possible applications of the results to crystal diffraction studies are discussed.