Changes in electronic structure of copper films in aqueous solutions

The possibilities for using x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) to probe the Cu oxidation state and changes in the electronic structure during interaction between copper and ground-water solutions were examined. Surface modifications induced by chemical reactions of oxidized 100 Å Cu films with Cl − , SO 4 2− and HCO 3 − ions in aqueous solutions with various concentrations were studied in situ using liquid cells. Copper corrosion processes in ground water were monitored for up to nine days. By comparing Cu 2p–3d, 4s transitions for a number of reference substances previously measured, changes in electronic structure of the Cu films were analysed. The XAS and RIXS spectral shape at the Cu edge, the chemical shift of the main line for Cu 2+ , and the energy positions of the observed satellites served as a tool for monitoring the changes during the reaction. It was found that the pH value and the Cl − concentration in solutions strongly affect the speed of the corrosion reaction.