CORE-HOLE SCREENING AND ELECTRONIC-STRUCTURE INFORMATION

Understanding the nature of core hole screening is fundamental for interpretation of the results of electron spectroscopies of metals and alloys. The idea of complete screening of the core hole explains a large amount of XPS and high resolution Auger (XAES) data. Here, we address the question of the extent to which the complete screening model can be used to extract quantitative information about the electronic structure of metals and their alloys from measured Auger energies. Starting from general considerations, analysis of Auger parameter data illuminates the screening process throughout the 4d and 5d series, including the consequences of closing the d valence shell; the observed systematics are faithfully reproduced, quantitatively as well as qualitatively, in the 3d series as well; and parameters of a simple model consistent with complete screening which are extracted from the Auger parameter data are applicable to analysis of XPS and Auger shifts in alloys. Similar treatment of core level Auger shift data of the noble metal component in bimetallic alloys indicates the relation between the measured shifts, the relative Fermi energy (a usually unknown quantity involved in binding energy shifts) and the charge transfer. Consideration of various alloys (AuPd, CuPd, AgPd, AuCu, AuAg, and CuPt) implies a very small charge transfer and a unique determination of the relative Fermi energy. Use of noble metals as ''impurities'' in trimetallic alloys bears out these conclusions regarding charge transfer and Fermi energies.