XPS spectra and electronic structure of Group IA sulfates

The structure of XPS valence band spectra is in good agreement with cluster calculations of SO42− and HSO4− [A.A. Audi, P.M.A. Sherwood, Surf. Interface Anal. 29 (2000) 265]. While the energies of bisulfate bands are not influenced by the cation (H+, Na+ or K+), the sulfate ones experience an increase in bond ionicity and demonstrate the same binding energy shifts as the core levels.