Interpreting ab initio energy level calculations for the trivalent praseodymium ion using a parametrized crystal-field Hamiltonian

Abstract Crystal-field parameters are extracted from ab initio calculations of the energy level structure of the 4 f 2 and 4 f 5 d configurations for Pr 3 + as a free ion and doped into Ca F 2 and Lu 2 O 3 crystals. The parameters are compared to those derived from direct phenomenological fits to experimental levels. The ab initio crystal-field parameters are in good agreement with experiment. For the ab initio calculations the F 2 Coulomb parameter is consistently larger, and the electron correlation configuration interaction parameter α is up to a factor of three larger, than the experimental parameters. This is consistent with previous calculations that suggest that significant contributions to electron correlation arise from continuum states.