On the contribution of the diamagnetic coupling term to the two-body retarded dispersion interaction

The contribution of the leading diamagnetic coupling term to the retarded d ispersion interaction between a pair of neutral atoms or randomly oriented molecules in the ground electronic state, is investigated using the multipo lar formalism of non-relativistic quantum electrodynamics. Within this fram ework the interaction energy is viewed as arising from the exchange of two virtual photons and is calculated using conventional time-dependent perturb ation theory. Explicit expressions are presented for energy shifts involvin g the interaction of a diamagnetic species with (a) an electric-dipole pola rizable body, (b) a magnetic-dipole susceptible body, (c) an electric-quadr upole polarizable body and (d) another diamagnetic species. The resulting p otentials obtained are applicable for all separation distances beyond the e lectron overlap region. Also given are the limiting forms of the energy shi ft at large and small inter-atomic/molecular separations.