Theory of resonant inverse photoemission spectroscopy in Ce compounds: Selection rule and hybridization strength

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 4f(n) --> 3d(9)4f(n+2) --> 4f(n+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 4f(2) and 4f(3) configurations with a 3d core hole is to be reduced to similar to 1/3 for CeNi2 and similar to 1/2 for CeRh3 of that connecting the 4f(0) and 4f(1) configurations without the core hole, which dominantly determines the 4f ground state. A tentative calculation assuming the reduction of similar to 0.8 is performed for CeO2. The calculation is also extended to IPES at the 4d core thrshold for CeNi2.