EVALUATION OF WEAK EXCHANGE INTERACTIONS BETWEEN ATOMS OR IONS WITH ORBITALLY DEGENERATE GROUND-STATES

The projection operator associated with the atomic second quantization method in the analysis of the exchange interaction between two weakly-coupled atoms, is easily obtained on the basis of the technique of symmetric double-coset (SDC) expansion of permutation groups. Furthermore, it is shown that in the analysis of the exchange interaction, using the SDC technique and without assuming orthogonality between the orbitals of the interacting electrons, the extension from orbitally non-degenerate to orbitally degenerate atomic ground-state wavefunctions is straightforward. © 1979.