The relative scaling of multiple-wavelength anomalous dispersion data

A formula is presented for the calculation of the values of the |Fⁿ_h|, the structure-factor magnitudes in the absence of anomalous dispersion, from the observed structure-factor magnitudes, |F_λh| and |F_λh|, that are affected by anomalous dispersion and hence vary with wavelength. Since the values of the |Fⁿ_h| are independent of wavelength, the calculation can provide the basis for relatively scaling data that are collected at different wavelengths. Test calculations of the formula with use of accurate data indicate that the formula has the potential to scale relatively experimental data in multiple-wavelength anomalous-dispersion experiments involving heavy-atom-substituted macromolecules to accuracies of 1 or 2% or better.