Cross-peak-specific two-dimensional electronic spectroscopy
Intermolecular electronic coupling dictates the optical properties of molecular aggregate systems. Of particular interest are photosynthetic pigment-protein complexes that absorb sunlight then efficiently direct energy toward the photosynthetic reaction center. Two-dimensional (2D) ultrafast spectro...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 36; pp. 14203 - 14208 |
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Main Authors | , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
National Academy of Sciences
04.09.2007
National Acad Sciences |
Series | Multidimensional Ultrafast Spectroscopy Special Feature |
Subjects | |
Online Access | Get full text |
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Summary: | Intermolecular electronic coupling dictates the optical properties of molecular aggregate systems. Of particular interest are photosynthetic pigment-protein complexes that absorb sunlight then efficiently direct energy toward the photosynthetic reaction center. Two-dimensional (2D) ultrafast spectroscopy has been used widely in the infrared (IR) and increasingly in the visible to probe excitonic couplings and observe dynamics, but the off-diagonal spectral signatures of coupling are often obscured by broad diagonal peaks, especially in the visible regime. Rotating the polarizations of the laser pulses exciting the sample can highlight certain spectral features, and the use of polarized pulse sequences to elucidate cross-peaks in 2D spectra has been demonstrated in the IR for vibrational transitions. Here we develop 2D electronic spectroscopy using cross-peak-specific pulse polarization conditions in an investigation of the Fenna-Matthews-Olson light harvesting complex from green photosynthetic bacteria. Our measurements successfully highlight off-diagonal features of the 2D spectra and, in combination with an analysis based on the signs of features arising from particular energy level pathways and theoretical simulation, we characterize the dominant response pathways responsible for the spectral features. Cross-peak-specific 2D electronic spectroscopy provides insight into the interchromophore couplings, as well as into the energetic pathways giving rise to the signal. With femtosecond resolution, we also observe dynamical processes that depend on these couplings and interactions with the protein environment. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Edited by Robin M. Hochstrasser, University of Pennsylvania, Philadelphia, PA, and approved May 7, 2007 Present address: Institute of Physics of Charles University, 12116 Prague 2, Czech Republic. Author contributions: E.L.R and G.S.E. contributed equally to this work; E.L.R. and G.S.E. designed research; E.L.R., G.S.E., T.R.C., and T.K.A. performed research; R.E.B. isolated and purified FMO sample; E.L.R., G.S.E., T.M., and G.R.F. analyzed data; and E.L.R. and G.S.E. wrote the paper. |
ISSN: | 0027-8424 1091-6490 |
DOI: | 10.1073/pnas.0701201104 |