Relaxation energies of oxygen auger transitions in some oxides

Relaxation effects are of major importance in the so-called chemical shifts observed in XPS and AES. These chemical shifts mainly arise from changes in the electrostatic environment due to the field of the neighbouring atoms in the initial neutral state and from electron redistribution in the surrounding electron cloud in order to screen the final state holes of the excited atom. Using a three-step model for the Auger process, we succeeded in deriving cross-relaxation energies from the KLL spectrum of oxygen in oxides, provided a careful calibration of experimental binding and Auger kinetic energies is achieved. It has been shown that the extra-atomic relaxation energy increases with ionicity for oxides of non-transition metals. In the case of transition metal oxides, it has been found that the cross-relaxation energies are larger than for the other oxides; it is believed that this is due to a more efficient screening effect of the d-electrons of the neighbouring metal atoms.