Theory of hard X-ray resonant photoelectron emission and related spectra in mixed valence Ce compounds

Abstract

Analyses of hard X-ray resonant photoelectron emission spectroscopy (HAX-RPES) and related spectroscopies such as X-ray absorption spectroscopy (XAS) and resonant X-ray emission spectroscopy (RXES) are made for mixed valence Ce compounds with single impurity Anderson model. First, the spectra of Ce 2 p 3 / 2 XAS ( L 3 XAS) and the conventional Ce 3d X-ray photoelectron emission spectroscopy (XPS) are analyzed for CePd 7 , taking into account the bulk/surface sensitivity in XPS. Then it is shown that the bulk properties are more directly obtained from the Ce 3d HAX-RPES spectra, in which the Ce 2p–5d excitation is followed by the Ce 2p3d5d Auger decay. Furthermore, the Ce 3d HAX-RPES can reveal some hidden structures in the Ce L 3 XAS. From the analysis of the Ce HAX-RPES for CeRh 3 , we reveal the existence of the Ce 4 f 2 contribution in the L 3 XAS, and confirm an important role of the Coulomb interaction U fd between Ce 4f and 5d elctrons in the XAS structure. For ferromagnetic mixed valence Ce compound CeFe 2 , the spectra of the CeL 3 XAS and its magnetic circular dichroism (MCD-XAS) are analyzed, and the effect of U fd is also important in explaining the relative peak positions of the XAS and MCD-XAS. Finally, the MCD in RXES (MCD-RXES) is calculated for CeFe 2 , and it is predicted theoretically that the excitation spectrum of MCD-RXES can also reveal the hidden structure of the 4 f 2 configuration in the Ce L 3 XAS (and MCD-XAS) spectrum.