Auger parameters and screening mechanisms in the 4d and 5d metals.

Abstract

We report measurements of ${\mathit{L}}_{3}$${\mathit{M}}_{4,5}$${\mathit{M}}_{4,5}$ Auger spectra for Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, and Sb. Detailed calculations indicate that the spectra are well described by the intermediate-coupling scheme, as we illustrate for In. The notion that the core-hole states are completely relaxed implies that the Auger parameter is the sum of a slowly varying core term and a term that is sensitive to the valence-electron configuration but independent of the core-level identities, which seems to be borne out by the ${\mathit{L}}_{3}$${\mathit{M}}_{4,5}$${\mathit{M}}_{4,5}$ and ${\mathit{M}}_{5}$${\mathit{N}}_{4,5}$${\mathit{N}}_{4,5}$ Auger parameters. The theoretical systematics of a model involving the quasiatomic picture indicates that the valence-electron contribution to the Auger parameter can be isolated. Comparison of the ${\mathit{L}}_{3}$${\mathit{M}}_{4,5}$${\mathit{M}}_{4,5}$ and ${\mathit{M}}_{5}$${\mathit{N}}_{4,5}$${\mathit{N}}_{4,5}$ results is consistent with the idea that the d-band holes behave as core holes in the screening process. Furthermore, it appears that certain of the screening parameters can be extracted from the data, resulting in values in reasonable agreement with independent calculations and in good agreement with experiment. Calculations for the 5d series are in good agreement with experiment, and we illustrate the separate contributions to the Auger parameter and the influence of screening in this case.