Ytterbium L_III-edge anomalous scattering measured with synchrotron radiation powder diffraction

The use of synchrotron powder diffraction patterns to determine anomalous scattering contributions is described. The method is illustrated by the determination of f' of Yb at the Yb L_III absorption edge. Four data sets were collected with four wavelengths, fitted with Gaussian profiles and the integrated intensities used to determine by least-squares methods the crystal-structure parameters and the real part f' of the anomalous dispersion. The derived f' values had a precision of ± 0.2 electron units and averaged 32% higher than the Cromer-Liberman theoretical values.