Dispersion interactions between atoms involving electric quadrupole polarizabilities.

Abstract

Retarded van der Waals forces involving electric quadrupole polarizabilities are investigated in detail in order to resolve the recently published conflicting predictions of the forms of dispersion potentials. One of the predictions was based on an approximate evaluation of the energies obtained from dispersion theory techniques. These techniques avoided explicit reference to the detailed structure of the individual systems. In applications to specific cases, the scattering amplitudes were related to the multipole polarizabilities in an approximate way. The second prediction used conventional nonrelativistic quantum electrodynamics in which a proper account of electronic structure was made. In this paper two particular cases involving an electric quadrupole polarizable body A are analyzed in detail. In one case the second body B has an electric dipole polarizability, and in the other case it has an electric quadrupole polarizability. For these two cases explicit expressions for the true intermolecular dispersion potentials are derived. The analysis shows that in general it is necessary to take into account the internal structures of the interacting systems, both their geometry and their dynamics, in order to obtain the complete form of van der Waals forces in terms of the multipole polarizabilities for the systems. \textcopyright{} 1996 The American Physical Society.