Long-range retarded intermolecular forces

The retarded interactions between neutral molecules at very large separations are calculated by perturbation of the electromagnetic vacuum state. This state is represented by the Wheeler form of the electromagnetic vacuum functional. Besides the well-known Casimir attractive $R^{-7\mathrm{}}$ potential energy between polarizable bodies, the repulsive interaction between one electrically and one magnetically polarizable molecule proportional to $R^{-7\mathrm{}}$ is computed. Also the specific discriminating force between optically active molecules, with potential proportional to $R^{-9\mathrm{}}$, is shown to follow similar calculations. For isomeric molecules this force is repulsive for identical handedness and attractive between enantiomers.