The Auger parameter and the polarization energy: A simple electrostatic model

In this paper we discuss the core‐hole screening mechanisms in the framework of the model proposed by Veal and Paulikas. If only the polarization of the ligands contributes to the relaxation energy, the non‐local screening mechanism, then the Wagner Auger parameter shifts can be estimated by a simple electrostatic model that takes into account the number, the distance and the electronic polarizability of the first neighbours of the atom with the core hole. The model has been verified for several compounds, comparing the calculated polarization energies with the experimental values obtained via the Auger parameter data taken from the literature. The same approach cannot be applied to systems containing the late transition metal ions for which a local screening mechanism occurs by a charge transfer from the ligand to the spatially localized d levels. The Auger parameter obtained from the main core photoemission peak of the late transition metal ions is almost insensitive to the chemical nature of the ligand itself and the screening energy is similar to that observed in the metallic state. In this case, the relaxation energy can be estimated from the energy separation between the main and the satellite structures in the core photoemission peak.