Giant Coster-Kronig transitions and intrinsic line shapes of the anomalous Pd M45VV Auger spectrum of Pd/Ag(100) dilute surface alloys

The Pd M4VV and M5VV Auger spectra of the 0.1 ML Pd/Ag(100) dilute surface alloy have been measured using Auger-photoelectron coincidence spectroscopy. The M4VV spectrum indicates that Pd 3d(3/2) core holes have a Coster-Kronig decay rate that is approximately 10 times that of Pd metal. Our calculations show that this giant enhancement arises from the local electronic structure of excited Pd atoms at the surface. Anomalous features in the Auger line shape are similar to those seen in dilute bulk PdAg alloys, and these features in the M5VV and M4VV lines are in good agreement with theoretical predictions.     

The lineshape of the L2,3 VV Auger spectrum of silicon

An attempt is presented to understand the details of the lineshape of the Si L_2,3 VV Auger spectrum from the (111) surface in the 7 × 7 superstructure. In the experiments we have followed the variation of the lineshape induced by adsorption of O₂, H₂O, CO and by bombardment with 3 keV Ar⁺ ions, over a range from a small perturbation of the surface to major changes in surface structure. For small perturbations from the clean surface we were able to resolve changes in the local density of states at surface silicon atoms. By unfolding the experimental spectra, effective transition densities of states result, which compare quite closely with calculated densities of states, apart from a certain enhancement of surface features in the experiments. All peaks in the experimental spectra can be explained, based on densities of states at the surface of pure Si(111) (7 × 7) (91.8 and 84.8 eV), Si(111) + adsorbed oxygen (70.6 eV), SiO₂, (78.9 and 64.5 eV) and plasmon losses, at 71.0 and 57.5 eV for the clean surface.     

The M4,5- VV Auger spectrum of silver: An interpretation based on quasi-atomic final states

The M_4,5- VV Auger spectrum of silver has been studied under high-resolution conditions. The relative energies and intensifies of the Auger lines calculated for a 4 d⁸ final state configuration account well for the experimental spectrum. This quasi-atomic behaviour is due to the fact that the effective two-hole Coulomb interaction is larger than the bandwidth. The influence of the solid state on the width of the Auger lines is discussed.