Theory of Resonant Inverse Photoemission Spectroscopy in Ce Compounds: Selection Rule and Hybridization Strength

Abstract

We analyze the recently measured resonant inverse photoemission spectroscopy (IPES) at the Ce 3d threshold in CeNi₂ and CeRh₃, which corresponds to a superposition of 4fⁿ → 3d⁹4fⁿ⁺² → 4fⁿ⁺¹ processes with n = 0 and 1, and predict an expected resonant IPES in CeO₂ on the basis of the Anderson impurity model including the full multiplet effect. By discussing a difference in selection rule of the final state between off- and on-resonances, the observed difference in spectrum is interpreted. The analysis shows that the magnitude of 4f-ligand hopping integral connecting the 4f² and 4f³ configurations with a 3d core hole is to be reduced to -- 1/3 for CeNi₂ and -- 1/2 for CeRh₃ of that connecting the 4f⁰ and 4f¹ configurations without the core hole, which dominantly determines the 4f ground state. A tentative calculation assuming the reduction of -- 0.8 is performed for CeO₂. The calculation is also extended to IPES at the 4d core thrshold for CeNi₂.