CRYSTAL-FIELD SPLITTING OF THE RARE-EARTH ION MANIFOLDS AND ELECTRIC-FIELD GRADIENT IN CRYSTALS OF LANTHANUM HALIDES

There may be a regularity in the variation of the total crystal field splittings of the manifolds of the rare earth ions with the electric f ield gradient at the ion in the host crystal of a series of compounds. For the lower energy levels (less than 20000 cm(-1)), the total cryst al field splittings of the manifolds of the rare earth ions in the hos t crystals of the lanthanum halides, increase with increasing value of the electric field gradient V at the rare earth ion from LaBr3 to LaC l3 and LaF3. This qualitative regularity may be useful for assignment of the levels of the rare earth ions in a series of compounds and for predicting the possible magnitude of the total crystal field splitting s of the manifolds of the rare earth ions in these host crystals. Some examples have been given.