New approaches to chiral discrimination in coupling between molecules

Results in the coupling of chiral molecules are reviewed from elementary points of view and some new results are given. We show that interactions between chiral molecules can be treated by using molecular quantum electrodynamics in electric and magnetic dipole approximation in ways different from standard diagrammatic perturbation theory. The interactions are the dispersive coupling of ground-state chiral molecules and excitation transfer, with emphasis on chiral discrimination. For ground-state molecules the coupling is dealt with first by calculating the coupling, at all separation distances, of electric and magnetic dipoles induced in the two molecules by fluctuations in the vacuum radiation field. The second method is the response by one chiral molecule to the field generated by the other. Excitation transfer is treated as the response by the accepting ground-state molecule to the dipole field of the donor. A novel variant in finding the rate of excitation transfer is by using Poynting's theorem.