The effect of anomalous scattering by atom M, introduced to replace another atom, may be used to resolve the ambiguity in phase-angle determination by the isomorphous replacement method. The effect of anomalous scattering is to introduce a phase shift, which means in effect, to change the atomic scattering factor of atom M from a ‘’real’’ quantity, f, to a ‘’complex’’ one(f + Df’) + iDf’’.
