Extension of exciton-transport theory for transient grating experiments into the intermediate coherence domain

Transient grating experiments provide a powerful new probe for exciton motion in molecular systems. An earlier theory of exciton transport directed at these experiments is extended into the intermediate coherence domain. Diffusion-equation results existing in the literature are shown to emerge as particular cases of this theory. Practically usable expressions for observed signals are given for an arbitrary degree of exciton coherence, and it is shown how coherence may be measured from the observations in experiments.