title: Coherent Vibronic Coupling in Light-Harvesting Complexes from Photosynthetic Marine Algae.
abstract: Observations of long-lived coherences in photosynthetic light-harvesting complexes utilize short pulses with broad spectral bandwidths to coherently excite multiple transitions and coherent superpositions. In order to identify the role that such quantum effects might play in efficient energy transfer, however, an alternative approach is required. We have developed a technique for two-color photon echo spectroscopy to selectively excite the pathway of interest and measure its evolution in the absence of any other excitation. We use this technique to excite a coherence pathway in phycocyanin-645 from cryptophyte algae and measure the dynamics of this coherence. A decoherence time of 500 fs was measured, and clear signatures for strong coupling between the electronic states and phonon modes were observed, allowing coherent coupling between otherwise nonresonant transitions. This provides detailed experimental evidence of the long-lived coherences and the nature of the quantum mechanical interactions between electronic states and phonon modes in phycocyanin-645 from cryptophyte marine algae.
authors.forename: G H
authors.initials: GH
authors.lastname: Richards
authors.affiliation: School of Physics and Centre for Applied Medical Research, St. Vincents Hospital, The University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: K E
authors.initials: KE
authors.lastname: Wilk
authors.affiliation: School of Physics and Centre for Applied Medical Research, St. Vincents Hospital, The University of New South Wales , Sydney, New South Wales 2052, Australia.
authors.forename: P M G
authors.initials: PM
authors.lastname: Curmi
authors.affiliation: School of Physics and ARC Centre of Excellence for Coherent X-Ray Science, The University of Melbourne , Victoria 3010, Australia.
authors.forename: H M
authors.initials: HM
authors.lastname: Quiney
authors.forename: J A
authors.initials: JA
authors.lastname: Davis
keywords: cryptophyte; long-lived coherence; quantum coupling; ultrafast spectroscopy