High Resolution Spectra of Rare Earth Crystals.

Energy levels derived from the spectra of triply-ionized rare earths in hexagonal lanthanum trichloride single crystals have been reinterpreted using an expanded Hamiltonian including two- and three-body electrostatic and two-body magnetic effective operators in the free-ion part, and two-body crystal field operators added to the crystal interaction part. A method has been developed for dealing with the very large matrix dimensions encountered for ions in the middle of the series.