Relativistic f <-> f transitions in crystal fields: II. Beyond the single-configuration approximation

A relativistic model of f <----> f transitions introduced previously is com pleted here by the third-order contributions caused by electron correlation . The approach is based on the transformation of all tensor operators to th eir relativistic effective form; the final effective operators that act wit hin the 4f shell are derived by means of the so-called partial closure. The tensorial structure of the new effective operators, that are in general tw o-particle objects, is discussed and their reduced form is analysed in the light of the standard single-particle parametrization scheme of f <----> f transition spectra.