Particularities of rare earth electronic structure

Principal terms of REE ions are considered. Gradual filling 4f-shell is shown to be characteristic for ions of Ce3+-Lu3+ series, geometrically the shell is inner; 4f-electrons interact with all the other electrons and they schield external electrons from the effect of positive charge of the nucleus. Any changes in 4f-shell immediately affect energetics and geometrical dimensions of other, especially upper schielding shells. An analog effect is observed under spin-orbital interaction of 4f-electrons as well as under the effect of ligand field. In the previous case noticeable shears of gravity centres of terms are observed