X-ray intensity measurements on large crystals by energy-dispersive diffractometry. III. Fine structures of integrated intensities and anomalous scattering factors near theKabsorption edges in GaAs

The anomalous scattering factor f' + if” of GaAs very near the K absorption edges has been investigated with the stress on the following two points. One is the determination of f' from the measured f” values through the linear absorption coefficient by calculation with the dispersion relation. The other concerns the effect of fine structures in the anomalous scattering factor on the integrated reflexion powers R555 and R{ 555} in the two ranges of ± 20 eV near the Ga K and As K absorption edges. The agreement between these calculations and measurements of R values is fairly good; this fact justifies the application of the dispersion relation to the determination of the f' values near the edge. Some advantages of this application are pointed out in terms of, particularly, the phase determination of reflexions from crystals with unknown structures.