Impurity-ligand effects on the magneto-optically measured spin-orbit splitting of trapped electron centres

The spin-orbit interaction of F A -type centres (F A , Z 2 + ) has been studied experimentally and theoretically. It is found to have a greater anisotropy than anticipated from early experiments on F A (Na) centres. Nearest-neighbour impurities with sufficiently large spin-orbit interaction may dominate the effect to yield both negative and positive spin-orbit energies depending on the relative orientation of the centres and the measuring light beam.