Overlap and covalency contributions to lanthanide-ion spectral intensity parameters

Overlap and covalency contributions to 4f → 4f electric dipole transition amplitude parameters have been calculated and compared with electrostatic configuration interaction contributions. They are shown to be similar in magnitude but opposite in sign. Comparison with experimental results confirms the conclusion of Reid, Dallara and Richardson to the effect that 'dynamic' ligand polarisation also provides an important contributing mechanism. (author)