['For', 'instance', ',', 'in', 'widely', 'studied', 'light', '-', 'harvesting', 'complexes', ',', 'there', 'are', 'two', 'identifiable', 'forms', 'of', 'the', 'photosynthetic', 'antenna', 'molecule', 'bacteriochlorophyll', ',', 'with', 'absorption', 'bands', 'centred', 'on', '800', 'and', '850', 'nm', ';', 'it', 'has', 'been', 'shown', 'that', 'the', 'most', 'efficient', 'forms', 'of', 'energy', 'transfer', 'between', 'the', 'two', 'occurs', 'when', 'there', 'is', 'a', 'neighbouring', 'carotenoid', 'species', '5–7', '.']