High-Pressure Study of LIII Absorption Edges of Rare-Earth Mixed Valence Systems

Abstract

The LIII X-ray absorption spectra of the rare earth (RE) systems exhibit a characteristic peak at threshold. This peak (a so-called white line) arises from transitions from atomic 2p3/2 core levels into empty 5d states. Systematic studies of LIII spectra of the RE(Sm-Lu) give unambigous experimental evidence that its white line reflects ground-state properties of the absorbing atom. The anomalous features of the Ce edge are discussed below. The white lines of the 4fn RE systems are shifted by 6 – 10 eV towards higher energies relative to those of 4fn+1 RE systems. This shift is mainly due to the screening of the central potential by an additional 4f electron in the 4fn+1 configuration. The LIII spectra of RE mixed-valence systems exhibit a characteristic double bump structure [1,2], which consists of a superposition of two white lines, separated by about 6 – 10 eV. We derive the valence v = 2(3)+υ simply from the relative intensities of the two white lines, where υ denotes the fractional 4f occupation. In this paper we report results obtained from high pressure LIII-absorption experiments of SmS, EuPd2Si2 and CeAl2 (see also Ref. 3).KeywordsRare EarthWhite LineAnomalous FeatureHigh Energy SideValence InstabilityThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.