Experimental valuation of net atomic charge via XPS

A method is proposed for the valuation of net atomic charge in chemical com pounds, based on XPS measurements of two energy levels for the same atomic species and on the evaluation of their difference. This approach, by consid ering two core levels, allows us to cancel the Madelung term and any other external potential from the electrostatic equation that rules the chemical shift of the binding energy. In this way, it directly relates the experimen tal shift with the net charge on the considered atomic species. The approxi mation that Madelung potential does not vary significantly from one core le vel to another one is used. The method has been applied to solid compounds containing silicon and to aluminosilicates having different counter-ions an d different Si/Al ratios. The experimental data of net charges have been co mpared, where possible, with Pauling and Sanderson charges obtained from el ectronegativity data. Copyright (C) 2000 John Wiley & Sons, Ltd.