Influence of double-electron transitions on the EXAFSLedges of rare-earth systems

This work presents an x-ray-absorption study at the L edges of several rare-earth compounds. In both ${\mathit{L}}_1$-edge and ${\mathit{L}}_3$-edge spectra, anomalous features are clearly detected in the EXAFS region and have been associated with the creation of 2s4d and 2p4d double-core hole states, respectively. Comparison of theoretical calculations with the experiments are carried out using the results of explicit computation of cross sections for the allowed mainline (L edge) and double-electron (${\mathit{LN}}_{4,5}$ edges) which identify the transitions expected to be observable. In addition, the excitation energies of all of these allowed transitions are given. The influence of multielectron transitions on the EXAFS data analysis is discussed for several rare-earth-based systems. An estimate of the error introduced by neglecting the presence of double-electron transitions on coordination numbers and bond distances is given, based on these experimental data.