Mechanism for reversed photoemission core-level shifts of oxidized Ag

Density functional theory calculations and high-resolution core-level spectroscopy are used to explore the remarkable observation of decreased Ag 3d binding energy upon silver oxidation. The shift in Ag 3d binding energy is investigated at different degrees of oxidation and compared to results for Pd 3d, which exhibits a normal shift. Analysis of initial-state effects and valence electronic structure shows that the onsite Ag core potential is insensitive to oxidation despite a clear metal-to-oxygen charge transfer. The substantial negative shift for oxidized Ag is instead attributed to final-state effects as screening of the core-hole occurs in metal s states of bonding character.