Anomalous Scattering

The previous discussion made the assumption that the energy of the incident radiation was far away from any of the absorption energies of the atom. The theory of X-ray scattering by the electrons of an atom requires modification when this condition is no longer satisfied. It was shown (in an earlier section) that when copper X-ray radiation is used in conjunction with an iron sample, the phenomenon of X-ray fluorescence may be observed. Not only do the iron atoms fluoresce under these conditions, but their scattering factor is also modified according to the commonly used equation: