Exciton transfer in disordered molecular aggregates: Computer modeling of optical line shapes in ring bacteria antenna systems

The structure of the LH2 subunit Rps. acidophila consists of a ring of 9 alpha beta heterodimers with 18 B850 BChl molecules sandwiched between the alpha and beta subunits. For Frenkel excitons moving on the ring we investigate the influence of dynamic and static disorder on their optical line shapes. The dynamic and static disorders are taken into account by fluctuations of the local energies of the BChl molecules. The fluctuations are represented by dichotomic Markov processes with coloured noise. Comparison of our theoretical results with experimental observations indicates, that the strength of the local energy fluctuation Delta should be smaller than J/2. (C) 1998 Elsevier Science B.V. All rights reserved.