Appearance-Potential Study of Resonant Transitions in Lanthanides

Abstract

Soft x-ray appearance potential spectroscopy (SXAPS) is a high resolution core level technique for probing the local density of conduction band states of the solid surfaces. It exploits the abrupt changes in the total x-ray emission associated with the threshold for the excitation of core levels. The sharp increases in the total x-ray fluorescence are enhanced by potential modulation technique. SXAPS has been utilized to investigate the distribution of 4f states of the lanthanides. The spectra reflect the transitions of N4, 5 core electrons to unoccupied 4f states. These states split into a multiplet as a result of exchange interaction between the 4f electrons and 4d vacancy. Multiplicity of these configurations depends upon the number of 4f electrons. A systematic study of spectral features of the lanthanides does not reveal any regular or orderly changes unlike the spectra of 3d transition metals. These results confirm that the spectra of lanthanides are amenable to interpretation in terms of the atomic-like resonances involving exchange interaction rather than in terms of the continuous interband transitions. The experimental results are discussed in the light of the above theoretical considerations.KeywordsCore LevelIncident ElectronCore ElectronCore HoleLanthanide SeriesThese 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.