Phase diagram for the trapping kinetics of partially coherent excitons

The kinetics of exciton trapping within molecular assemblies similar to those of recently reported structural models of photosynthetic light-harvesting antennas have been described theoretically for any degree of exciton coherence. It is shown here that in the space of two of the kinetic parameters – the local exciton scattering rate constant and the nearest-neighbor separation distance of the exciton-generating transition dipoles – the trapping kinetics segregate into coherent and incoherent phases delineated by universal curves. Consequences of these findings are discussed, particularly as they may apply to purple photosynthetic bacteria.