Electron-Electron Correlation, Resonant Photoemission and X-Ray Emission Spectra

Abstract

In this short review paper we essentially focus on the high energy spectroscopies which involve second order quantum processes, i.e., resonance photoemission, Auger and X-ray emission spectroscopies, denoted respectively by RXPS, AES and XES. First, we summarize the main 3P-RXPS and AES results obtained in Cu and Ni metals; especially we recall that the satellite near the 3P-threshold in the spectra, which arises from a d-hole pair bound state, needs a careful treatment of the electron-electron correlation. Then we analyze the RXPS spectra in a few Ce compounds (Ce02, Ce20a and CeFa) involving 3d or 4d core levels and we interpret the spectra consistently with the other spectroscopies, such as core XPS and XAS which are first order quantum processes. Finally within the same one-impurity model and basically with the same sets of parameters, we review a theory for the Ce 5p-+ 3d XES, as well as for the corresponding RXES, where (1) the incident X-ray is tuned to resonate with the 3d -+4! transition and (2) the X-ray emission due to the 5p-+3d transition is actually observed. The paper ends with a general discussion.