FEMTOSECOND ENERGY-TRANSFER AND SPECTRAL EQUILIBRATION IN BACTERIOCHLOROPHYLL A-PROTEIN ANTENNA TRIMERS FROM THE GREEN BACTERIUM CHLOROBIUM-TEPIDUM

Femtosecond energy transfer processes in a bacteriochlorophyll a-prote in antenna complex from the green sulfur bacterium Chlorobium tepidum have been studied by one-color, two-color, and broadband absorption di fference spectroscopy. Much of the spectral excitation equilibration i n this antenna occurs with 350 to 450 fs kinetics. The anisotropy deca y functions r(t) exhibit two major lifetime components, 100 to 130 fs and 1.7 to 2.0 ps. The short component lifetimes may represent single- step energy transfer kinetics in this antenna; the long component is s imilar to the anisotropy decay observed in earlier picosecond pump-pro be experiments.