title: Towards quantification of vibronic coupling in photosynthetic antenna complexes.
abstract: 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.
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: V P
authors.initials: VP
authors.lastname: Singh
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: M
authors.initials: M
authors.lastname: Westberg
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.affiliation: Graduate Program in the Biophysical Sciences, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: P D
authors.initials: PD
authors.lastname: Dahlberg
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: T
authors.initials: T
authors.lastname: Gellen
authors.affiliation: Department of Botany, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, Scotland.
authors.forename: A T
authors.initials: AT
authors.lastname: Gardiner
authors.affiliation: Department of Botany, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, Scotland.
authors.forename: R J
authors.initials: RJ
authors.lastname: Cogdell
authors.affiliation: Department of Chemistry, The James Franck Institute and The Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: G S
authors.initials: GS
authors.lastname: Engel
mesh_terms: D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism*; D010788:Photosynthesis; D011789:Quantum Theory; D012242:Rhodobacter sphaeroides / Q000737:chemistry* / Q000378:metabolism; D014732:Vibration
chemical_list: D045342:Light-Harvesting Protein Complexes