We discuss, from a classical as well as a quantum-mechanical point of view, the effect of the coupling of an excited two-level system with itself due to emission and absorption of electric-dipole radiation, the emitted radiation being reflected by a nearby mirror. Expressions familiar from resonance-scattering theory are found for the shift of the transition frequency and linewidth from their values in the absence of the mirror. This renormalization effect leads to spatial modulation in the transition frequency and width of the excited state due to its resonant interaction with itself via the radiation field reflected from the mirror. This formalism is applied to some recent experiments with monomolecular dye layers. The experimental values of the fluorescence lifetime are in good agreement with the theory for distances from 500 to 6000 Å.

• Received 1 April 1969

DOI:https://doi.org/10.1103/PhysRev.187.1792