Virtual polariton modes of slab molecular crystals

The virtual polariton states of a slab dielectric consisting of N planes of discrete molecules are considered using the dipole approximation for intermolecular interactions. It is assumed that the sum of in-plane static interactions is large compared to the inter-plane sums. The dispersion relation of the virtual modes is solved for exactly and the conditions defined under which it reduces to the dispersion relations for symmetric and antisymmetric modes of a slab of continuous matter. Finally some comments are made on the occurrence of virtual polariton states in fluorescence and absorption processes.