Theory of the time evolution of exciton coherence in weakly disordered crystals

Abstract
Coherent states in molecular crystals are described as minimum‐uncertainty superpositions of all the crystal states that can interact with light, and their amplitude decay due to the presence of disorder is calculated through the time‐dependent exciton Greens function. The functional form of the decay is investigated, and different methods for its calculation are compared. The decay obtainable for the k=0 vibrational exciton in α‐N2 through direct time‐domain approximations provides good agreement with experimental results.