Excitons in core LH1 antenna complexes of photosynthetic bacteria: Evidence for strong resonant coupling and off-diagonal disorder

Abstract The structure of the exciton manifold in the core bacteriochlorophyll antenna complexes from the purple photosynthetic bacterium Rhodobacter sphaeroides has been studied at 5 K using conventional and polarized fluorescence excitation spectroscopy supported with model simulations. Exciton bandwidths in the range of 2100–2200 cm −1 , depending on sample integrity, have been determined in correlation with the largest mean coupling energy between the nearest-neighbor bacteriochlorophyll molecules close to 600 cm −1 . These numbers are considerably bigger than those in any other native antenna complex known. Another noteworthy feature of these complexes is dominance of structural (off-diagonal) static disorder over the energetic (diagonal) disorder.

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