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

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 2p3/2 XAS (L3 XAS) and the conventional Ce 3d X-ray photoelectron emission spectroscopy (XPS) are analyzed for CePd7, 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 L3 XAS. From the analysis of the Ce HAX-RPES for CeRh3, we reveal the existence of the Ce 4f2 contribution in the L3 XAS, and confirm an important role of the Coulomb interaction Ufd between Ce 4f and 5d elctrons in the XAS structure. For ferromagnetic mixed valence Ce compound CeFe2, the spectra of the CeL3 XAS and its magnetic circular dichroism (MCD-XAS) are analyzed, and the effect of Ufd 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 CeFe2, and it is predicted theoretically that the excitation spectrum of MCD-RXES can also reveal the hidden structure of the 4f2 configuration in the Ce L3 XAS (and MCD-XAS) spectrum.