Ƒ-electron Correlations in Nonmagnetic Ce Studied by Means of Spin-Resolved Resonant Photoemission

We have studied the spin-spin coupling between two f electrons of nonmagnetic Ce by means of spin-resolved resonant photoemission using circularly polarized synchrotron radiation. The two f electrons participating in the 3d5/2-->4f resonance process are coupled in a singlet while the coupling is veiled in the 3d3/2-->4f process due to an additional Coster-Kronig decay channel. The identical singlet coupling is observed in the 4d-->4f resonance process. Based on the Ce measurements, it is argued that spin-resolved resonant photoemission is one approach to study the correlation effects, particularly in the form of spin, in the rare earths.