POLARONS, LOCALIZATION, AND EXCITONIC COHERENCE IN SUPERRADIANCE OF BIOLOGICAL ANTENNA COMPLEXES

A real-space formulation of time-resolved fluorescence of molecular ag gregates is developed using the one-exciton density matrix rho(t) of t he optically driven system. A direct relationship is established betwe en the superradiance enhancement factor L-s, and the exciton coherence size L-rho associated with the off-diagonal density matrix elements i n the molecular representation. Various factors which affect the latte r, including finite temperature, energetic disorder, coupling with pho nons, and polaron formation are explored. The theory is applied for th e interpretation of recent measurements in the B850 system of the LH2 photosynthetic complexes. (C) 1997 American Institute of Physics.