Three-Body Dispersion Energy Shift: Contributions from Higher Electric Multipoles

Employing the Craig-Power Hamiltonian, a general formula is obtained for the retarded dispersion energy shift among three arbitrarily electrically polarisable atoms or molecules. Explicit expressions are then extracted for the first few leading order corrections to the triple dipole potential. These include energy shifts in which two of the particles are electric dipole polarisable and the third is either electric quadrupole or octupole polarisable, as well as the interaction between an electric dipole polarisable atom and two electric quadrupole polarisable ones. Results are obtained for arbitrary three-body configurations, and for equilateral triangle and collinear arrangements. In each case, near- and far-zone asymptotes are computed.