Importance of dynamical effects in determining the Auger spectral shape: L23-M45M45 spectra of Fe, Co, and Cu

Measuring Charge Transfer between Adsorbate and Metal Surfaces

Charge transfer between dissimilar atoms is an essential step for many chemical processes such as corrosion and heterogeneous catalysis, but directly probing the charge transfer has been a challenge. Using the oxygen-copper system as an example, we show that synchrotron-based ambient pressure X-ray photoelectron spectroscopy can be employed to monitor the charge transfer between adsorbates and metal surfaces. It is shown that oxygen chemisorption on Cu surfaces results in an Auger process that differs from the photoexcitation-induced Coster-Kroning transition and can be used to derive the degree of charge transfer in combination with ab initio calculations. The identified chemisorption-induced Auger process may have broader implications for its use as a fingerprint to monitor bond formation and charge transfer between dissimilar atoms.

Final state interaction observed in M(2,3)VV Auger profile of Cu(110)

We have measured the M(2,3)VV Auger spectra of Cu(110) and studied the final state interaction following the Cu 3p core electron excitation. We have observed that the kinetic energy of the M(2,3)VV Auger electron shifts to an energy higher than that of the normal Auger electrons near the Cu 3p threshold, and it converges to the constant kinetic energy of the normal Auger electrons as the excitation energy increases above the Cu 3p threshold. In the excitation energy dependence of the kinetic energies of the M(2,3)VV Auger electrons, we observed step features at the excitation energies corresponding to the 3p core electron excitations to the L(1) and X(1) van Hove singularities in the valence states. The kinetic energy shifts of the M(2,3)VV Auger electrons are reasonably understood by considering the localization of the two-hole Auger final state and the hybridization between Cu 3d states and other valence states.