Interpretation of the nitrogen K V V Auger line shape from alkali metal nitrates

Abstract

Experimental N KVV Auger line shapes from sodium nitrate, produced by both x-ray (XEA) and electron (EEA) excitation, are compared to theoretically derived line shapes based on populations derived from a GTO-LCAO-Xα model. The one-electron orbital energies and valence line widths are determined from x-ray emission and photoelectron data; the Auger matrix elements are determined from experimental gas phase atomic Auger data. The theoretical Auger energies include hole–hole repulsion and relaxation. Theoretical lines shapes using the local and the Mulliken Xα populations are generated, and a set of empirical populations are also determined. This work emphasizes the importance of shake-off arising from creation of the initial core hole and its effect on the Auger line shape. A theoretical shake/Auger satellite line shape is generated and found to contribute up to 35% of the total intensity. The XEA and EEA line shapes (after correction for the sample and spectrometer transmission response) each show five features, but some differences are noted. These are attributed primarily to beam damage and charging effects on the EEA line shape. The theoretical line shapes reproduce the five principal features of the experimental spectra; specific features in the line shape are shown to reflect the relative size of the Auger matrix elements, the symmetry of the NO−3 ion, and satellite contributions. Arguments for the validity of a one-electron orbital model to describe the Auger line shape are presented.