CHEMICAL-STATE INFORMATION FROM PHOTOELECTRON AND AUGER-ELECTRON LINES - INVESTIGATION OF POTENTIAL AND RELAXATION EFFECTS OF SOLID SILICON AND PHOSPHORUS-COMPOUNDS

Measured chemical shifts of photoelectron and Auger electron energies of solid silicon and phosphorus compounds are used for determination of potential energy and relaxation energy shifts. The trends of these shifts and their dependences on parameters characterizing the chemical bond and on the atomic number are discussed. It was shown that the trends of relaxation energy shifts for both silicon and phosphorus compounds are the same. However, the trends of potential shifts of these two elements in their compounds are different depending on the atomic contribution to the potential effect. The observed larger relaxation energy values of the solids in comparison with volatile molecules are caused by the Madelung contribution of higher coordination spheres. Theoretical estimates of relaxation energies using an extended version of the Fenske-Hall method and taking into account the charge of the molecular potential term give an excellent correlation with experimental values. The Shirley approach for determination of potential energy and relaxation energy shifts proves to be a sensitive method for describing electronic changes when atoms combine to form molecules or solids. It is able to distinguish between the atomic term and the surroundings term (Madelung term) of the chemical shift.