Oscillating anisotropies in a bacteriochlorophyll protein: Evidence for quantum beating between exciton levels

摘要: Abstract Optical anisotropies of bacteriochlorophyll a Qy electronic transitions in Fenna-Matthews-Olson trimers from the green photosynthetic bacterium Chlorobium tepidum eshibit strong oscillations with ∼ 220 fs period for certain wavelengths one-color absorption difference experiments. The polarized pump-probe signals Δ A∥(t), A⊥] (t) have opposite phase, and they nearly cancel isotropic signals. This combined fact that only appear when laserpulse spectrum overlaps both lowest-energy groups excitation levels clustered near 815 825 nm, suggests stem quantum beating between exciton levels, rather than coherent nuclear motion. In some cases, anisotropy r(t) exhibits values > 0.4 at times well beyond laser autocorrelation function.