Determination of odd-symmetry crystal-field parameters from optical spectra

We have obtained analytical expressions for effective parameters of the crystal field that acts on spin-orbit multiplets of 4fN configurations taking into account admixture to them of 4fN−15d excited states and ligand-to-metal charge-transfer states. As an example, we analyze splittings of the ground and excited multiplets of Pr3+ and Tm2+ ions in some crystals without an inversion center. The effect of mixing of states of different configurations is most strongly pronounced for the 1G4 and 1D2 excited multiplets. The interconfigurational contribution to splittings is different for different multiplets. This circumstance makes it possible to estimate the values of the parameters of the odd-symmetry crystal field, which causes mixing of the 4fN and 4fN−15d states, and the covalence parameters of rare-earth ion-ligand bonds.