Satellite structure in photoelectron and Auger spectra of copper dihalides

The satellite structure of core photoelectron and Auger lines of the copper dihalides are explained in terms of final-state energies diminished by Coulomb interactions between the valence electrons and the created core hole or holes. The satellite structure in the $3p$ and valence-band photoelectron spectra are shown to originate from the same final states as the $L_3{M}_{23}{M}_{45}$ and $L_3{M}_{45}{M}_{45}$ main Auger lines. The energies of the main core lines are shown to yield information about the valence ligand binding energies and therefore are sensitive to chemical shifts. The satellite lines are rather insensitive to chemical shifts but their intensities yield information concerning the relative positions of the Cu $3d$ and ligand valence holes and the amount of hybridization. In terms of the core line photoelectron and Auger spectra we show that an assignment can be made of the valence-band spectra. From a combination of all the results we conclude that especially Cu${\mathrm{Cl}}_2$ and Cu${\mathrm{Br}}_2$ are strongly covalent and we predict that in Cu${\mathrm{I}}_2$ the valence hole would be predominantly in the I $5p$ level which is probably the reason why this material is not stable.