A simple route to the energy shift between an electrically polarizable molecule and a magnetically susceptible molecule via the electromagnetic energy density

Abstract

The van der Waals dispersion interaction between a molecule that is electrically polarizable and one that is magnetically susceptible, is recalculated within the framework of non-relativistic quantum electrodynamics. The energy shift is obtained in a simple way by calculating the response of a test polarizable body to the electromagnetic energy density due to a second source molecule. It is confirmed that the near-zone asymptote of the potential between an electric dipole polarizable molecule and a paramagnetic one varies as R ^{− 4}. Inclusion of the often neglected diamagnetic coupling term, however, results in an R ⁻⁵ dependent short-range behaviour, which is seen to dominate over the paramagnetic contribution in the near-zone. For larger intermolecular distances, the expected R ⁻⁷ dependence on separation is found for both paramagnetic and diamagnetic susceptible molecules interacting with an electric dipole polarizable one.