Coherent Oscillations in Chlorosome Elucidated by Two-Dimensional Electronic Spectroscopy.
Chlorosomes are the most efficient photosynthetic light-harvesting complexes found in nature and consist of many bacteriochlorophyll (BChl) molecules self-assembled into supramolecular aggregates. Here we elucidate the presence and the origin of coherent oscillations in chlorosome at cryogenic temperature using 2D electronic spectroscopy. We observe coherent oscillations of multiple frequencies superimposed on the ultrafast amplitude decay of 2D spectra. Comparison of oscillatory features in the rephasing and nonrephasing 2D spectra suggests that an oscillation of 620 cm(-1) frequency arises from electronic coherence. However, this coherent oscillation can be enhanced by vibronic coupling with intermolecular vibrations of BChl aggregate, and thus it might originate from vibronic coherence rather than pure electronic coherence. Although the 620 cm(-1) oscillation dephases rapidly, the electronic (or vibronic) coherence may still take part in the initial step of energy transfer in chlorosome, which is comparably fast.
†Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 305-701, Republic of Korea.|‡Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea.
Sunhong
S
Jun
†Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 305-701, Republic of Korea.|‡Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea.
Cheolhee
C
Yang
§Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
Megumi
M
Isaji
§Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
Hitoshi
H
Tamiaki
∥Department of Chemistry, Inha University, Incheon 402-751, Republic of Korea.
Jeongho
J
Kim
†Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 305-701, Republic of Korea.|‡Department of Chemistry, KAIST, Daejeon 305-701, Republic of Korea.
Hyotcherl
H
Ihee
chlorosome; coherent oscillation; electronic coherence; energy transfer; two-dimensional electronic spectroscopy