Towards quantification of vibronic coupling in photosynthetic antenna complexes

Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coh...

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Bibliographic Details
Published in:The Journal of chemical physics 2015-06, Vol.142 (21), p.212446-212446
Main Authors: Singh, V P, Westberg, M, Wang, C, Dahlberg, P D, Gellen, T, Gardiner, A T, Cogdell, R J, Engel, G S
Format: Article
Language:English
Subjects:
ANTENNAS
BIOCHEMISTRY
Chromophores
COMPLEXES
COUPLING
Coupling (molecular)
EFFICIENCY
Electron states
Energy
ENERGY GAP
Energy storage
ENERGY TRANSFER
GROUND STATES
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
Light-Harvesting Protein Complexes - chemistry
Light-Harvesting Protein Complexes - metabolism
MOLECULES
PHOTOSYNTHESIS
Physics
Power efficiency
POWER TRANSMISSION
Quantum phenomena
Quantum Theory
Rhodobacter sphaeroides - chemistry
Rhodobacter sphaeroides - metabolism
Special Topic: Multidimensional Spectroscopy
Vibration
VIBRATIONAL STATES
VISIBLE RADIATION
Wave packets
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Summary:Photosynthetic antenna complexes harvest sunlight and efficiently transport energy to the reaction center where charge separation powers biochemical energy storage. The discovery of existence of long lived quantum coherence during energy transfer has sparked the discussion on the role of quantum coherence on the energy transfer efficiency. Early works assigned observed coherences to electronic states, and theoretical studies showed that electronic coherences could affect energy transfer efficiency--by either enhancing or suppressing transfer. However, the nature of coherences has been fiercely debated as coherences only report the energy gap between the states that generate coherence signals. Recent works have suggested that either the coherences observed in photosynthetic antenna complexes arise from vibrational wave packets on the ground state or, alternatively, coherences arise from mixed electronic and vibrational states. Understanding origin of coherences is important for designing molecules for efficient light harvesting. Here, we give a direct experimental observation from a mutant of LH2, which does not have B800 chromophores, to distinguish between electronic, vibrational, and vibronic coherence. We also present a minimal theoretical model to characterize the coherences both in the two limiting cases of purely vibrational and purely electronic coherence as well as in the intermediate, vibronic regime.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4921324