, and ℎ𝜈𝜈 is the external photoenergy of chromophore excitation. Although the main goal of this study is concerned with excimers, we nevertheless use different symbols X and Y to denote the two interacting molecules for convenience of discussion. Thus, the theory is generally applicable to exciplexes in which 𝑋𝑋 ≠ 𝑌𝑌. Also, the method can easily be generalized to any number of molecules, suitable for the treatment of delocalized, exciton-resonance excitation of extended materials and biological light-harvesting systems.