Photoemission from Yb: Valence-change-induced Fano resonance

Abstract

Photoemission and photon-absorption results on clean and oxidized Yb are presented that clearly reveal a difference in $4f$ occupancy between the clean ($4{f}^{14}$) and oxidized ($4{f}^{13}$) case. For the oxidized metal a resonance enhancement of the $4f$-electron emission is observed at the $4d$ threshold. The enhancement arises from autoionization decay following $4d\ensuremath{\rightarrow}4f$ absorption transitions. The resulting line profile is shown to be well described by Fano's theory of interaction between a discrete and continuum state.