Strong4fResonance Effects in Rare-Earth Appearance-Potential Spectra

Abstract
Soft-x-ray appearance-potential spectra of rare-earth elements are interpreted in terms of strong resonance interactions between the incident electrons and atomic 4f states. These interactions account for both the large intensity and the threshold shifts of the measured signal. This resonance persists in La, Ce, Pr, and Nd when present as only a few atomic percent in a NiCr alloy reflecting the local character of the interaction.