Dipole moments of ligands and stark splitting of levels of rare-earth ions

A model for describing polarization and relaxation of ligand ions around impurity defects in crystals is proposed and tested. This approach is based on the introduction of effective electric dipole moments, which are considered to be fundamental parameters of crystals and are determined from experimental data on the energy-level structure of an impurity ion. Calculations performed for rare-earth ions show that their energy spectra depend strongly on the effective electric dipole moments of host-crystal ions surrounding the impurity ions. Parameters of the theory are found. The results of the calculations are consistent with the available experimental data. The possibility of using the considered approach in studies of impurity defects in various crystals (semiconductors and insulators) is discussed. (C) 2001 MAIK "Nauka/Interperiodica".