The measurable effects of anomalous scattering

When the X-ray wavelength is near the heavy-atom absorption edge, a fraction of the radiation is absorbed by the heavy atom and re-emitted with altered phase. The effect of this anomalous scattering on a given structure factor fhp in the heavy-atom data is depicted in vector diagrams as consisting of two perpendicular contributions, one real (AFr) and the other imaginary (AFj). 

In Fig. 6.11, F p represents a structure factor for the heavy atom derivative measured at wavelength where anomalous scattering does not occur. F p is the same structure factor measured at a second X-ray wavelength X2 near the absorption edge of the heavy atom, so anomalous scattering alters the heavy-atom contribution to this structure factor. The vectors representing 

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