DISTRIBUTION OF IONS IN SUBSURFACE LAYERS OF LIQUID SOLUTIONS STUDIEDBY ARXPS

A numerical method for generating depth concentration profiles on the basis of angular resolved XPS data has been applied to the study of a classical physico-chemical phenomenon, i.e. the formation of electric double layers in fatty acid salts solutions in polar liquids. Results from investigations of solutions of potassium octanoate in formamide a nd ethylene glycol are presented. The characteristic features of a dou ble layer structure are confirmed from the calculations, with a strong ly segregated anion overlayer and an underlying mainly diffuse cation distribution in the subsurface layers. At higher bulk concentrations e vidence is found for the formation of contact pairing in the uppermost surface layer.