Origin of long-lived coherences in light-harvesting complexes.
A vibronic exciton model is applied to explain the long-lived oscillatory features in the two-dimensional (2D) electronic spectra of the Fenna-Matthews-Olson (FMO) complex. Using experimentally determined parameters and uncorrelated site energy fluctuations, the model predicts oscillations with dephasing times of 1.3 ps at 77 K, which is in a good agreement with the experimental results. These long-lived oscillations originate from the coherent superposition of vibronic exciton states with dominant contributions from vibrational excitations on the same pigment. The oscillations obtain a large amplitude due to excitonic intensity borrowing, which gives transitions with strong vibronic character a significant intensity despite the small Huang-Rhys factor. Purely electronic coherences are found to decay on a 200 fs time scale.
Faculty of Physics, University of Vienna, Strudlhofgasse 4, 1090 Vienna, Austria.
Niklas
N
Christensson
Harald F
HF
Kauffmann
Tõnu
T
Pullerits
Tomáš
T
Mančal
D001426:Bacterial Proteins / Q000737:chemistry*; D041883:Chlorobium / Q000737:chemistry*; D004583:Electrons; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D011789:Quantum Theory
D001426:Bacterial Proteins; C086320:FMO bacteriochlorophyll protein, Bacteria; D045342:Light-Harvesting Protein Complexes