Eur. Phys. J. B (2012) 85: 257
https://doi.org/10.1140/epjb/e2012-30079-1

Regular Article

Spectator and participator processes in the resonant photon-in and photon-out spectra at the Ce L₃ edge of CeO₂

¹ Photon Factory, Institute of Materials Structure Science, 1-1 Oho, Tsukuba, 305-0801 Ibaraki, Japan
² RIKEN SPring-8 Center, 1-1-1 Kouto, Mikazuki-cho, Sayo-gun, 679-5148 Hyogo, Japan
³ European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP 220, 38043 Grenoble, France
⁴ Department of Physics and Astronomy, Uppsala University, Box 516, 75120 Uppsala, Sweden

^a e-mail: kotani@post.kek.jp

Received: 1 February 2012
Received in final form: 10 May 2012
Published online: 30 July 2012

Abstract

We study both theoretically and experimentally the photon-in and photon-out spectra of CeO₂, which are caused by the Ce 2p to Ce 5d excitation followed by the three different de-excitation channels: (i) Ce 3d to Ce 2p (denoted by 3d-RXES), (ii) O 2p to Ce 2p (v-RXES), and (iii) Ce 5d to Ce 2p (RIXS). In 3d- and v-RXES, the 5d electron plays a role of a spectator, but in RIXS it is a participator. By extending our single impurity Anderson model (SIAM), which was used recently for our calculations of v- and 3d-RXES spectra of CeO₂, we study the polarization dependence in the spectator and participator spectra, and we perform more detailed calculations for 3d- and v-RXES spectral features, as well as new calculations for the RIXS spectrum with charge transfer excitations. The polarization dependence is different for the spectator and participator spectra; we have no polarization correlation between the incident and emitted photons for the spectator spectra but a strong polarization correlation for the participator spectrum. The theoretical calculations predict that the charge transfer excitations in RIXS occur in the transfer-energy range overlapped with v-RXES, but the RIXS and v-RXES spectra can be discriminated by taking advantage of the different polarization dependence. The overlapped RIXS and v-RXES spectra are observed successfully by our experiments and well reproduced by our SIAM calculations.