Abstract :
In the backbonding energy region of adsorbate Auger spectra, the deexcitation processes involving the screening electron, can lead to a one-hole-like final state instead of a two-hole final state. The “negative” U invoked for the two-hole final state of CO adsorbed systems is explained in terms of the presence of the one-hole-like final state. The relaxation of the resonantly core level excited neutral state to the core level ionized state by the “shakedown” of the resonantly excited electron to the ligand character screening orbital (instead of delocalization of the electron to the empty substrate band) leads to the participant decay of the bonding level close to the Fermi level.
