Application of the correlation-crystal-field delta-function model in analyses of Pr3+(4f2) energy-level structures in crystalline hosts Original Research Article

The 4f2 electronic energy-level structures observed for Pr3+ in seven different crystalline host materials are analyzed and compared. The analyses are based on a model Hamiltonian that includes consideration of both one-electron crystal-field (CF) and two-electron correlation-crystal-field (CCF) interactions. Special attention is given to the importance of CCF interactions in determining the crystal-field energy-level structures observed within particular anomalous multiplet manifolds of Pr3+, such as the 1D2 and 1G4 multiplets, which typically exhibit crystal-field energy-level structures that cannot be explained in terms of `standardʹ one-electron CF interaction models. It is shown in the present study that the apparently anomalous behavior of these multiplets can be explained in terms of two-electron CCF effects. It is further shown that the relevant CCF effects can be satisfactorily modeled by use of a highly restricted `delta-functionʹ form of the general two-electron CCF model Hamiltonian, where the dominant two-electron correlation effects are assumed to arise from spin-paired electrons occupying the same angular orbital. Incorporation of this restricted CCF model Hamiltonian into the modeling calculations requires the introduction of only one or two additional parameters beyond those required for the standard one-electron CF modeling calculations, and satisfactorily resolves the major discrepancies between observed and calculated crystal-field splittings for the anomalous 1D2 and 1G4 multiplet manifolds in the energy-level structures of LaCl3:Pr3+, GdCl3:Pr3+, Cs2NaPrCl6, Cs2NaYCl6:Pr3+, LiYF4:Pr3+, LiBiF4:Pr3+, and CsCdBr3:Pr3+.