A simple model for the f–d transition of actinide and heavy lanthanide ions in crystals

The original simple model for 4f–5d transitions [C.K. Duan, M.F. Reid, G.W. Burdick, Phys. Rev. B 66 (2002) 155108; C.K. Duan, M.F. Reid, J. Solid State Chem. 171 (2003) 299], which assumes a stronger exchange Coulomb interaction between 4f orbitals and 5d orbitals than the 4f spin–orbit interaction, is extended to the case where the effect of the f (4f for heavy lanthanide and 5f for actinide ions) spin–orbit interaction is stronger than that of the exchange Coulomb interaction. The extended model is used to discuss the 4f–5d spectra of heavy lanthanide and actinide ions in crystals.