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Before Förster. Initial excitation in photosynthetic light harvesting

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Abstract

Electronic 2D spectroscopy allows nontrivial quantum effects to be explored in unprecedented detail. Here, we apply recently developed fluorescence detected coherent 2D spectroscopy to study the light harvesting antenna 2 (LH2) of photosynthetic purple bacteria. We report double quantum coherence 2D spectra which show clear cross peaks indicating correlated excitations. Similar results are found for rephasing and nonrephasing signals. Analysis of signal generating quantum pathways leads to the conclusion that, contrary to the currently prevailing physical picture, the two weakly coupled pigment rings of LH2 share the initial electronic excitation leading to quantum mechanical correlation between the two clearly separate absorption bands. These results are general and have consequences for the interpretation of initially created excited states not only in photosynthesis but in all light absorbing systems composed of weakly interacting pigments where the excitation transfer is commonly described by using Förster theory. Being able to spectrally resolve the nonequilibrium dynamics immediately following photoabsorption may provide a glimpse to the systems' transition into the Förster regime.

Graphical abstract: Before Förster. Initial excitation in photosynthetic light harvesting

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Publication details

The article was received on 17 Apr 2019, accepted on 04 Jul 2019 and first published on 04 Jul 2019


Article type: Edge Article
DOI: 10.1039/C9SC01888C
Chem. Sci., 2019, Advance Article
  • Open access: Creative Commons BY-NC license
    All publication charges for this article have been paid for by the Royal Society of Chemistry

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    Before Förster. Initial excitation in photosynthetic light harvesting

    K. J. Karki, J. Chen, A. Sakurai, Q. Shi, A. T. Gardiner, O. Kühn, R. J. Cogdell and T. Pullerits, Chem. Sci., 2019, Advance Article , DOI: 10.1039/C9SC01888C

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