Source: https://www.nature.com/articles/nphys3017?error=cookies_not_supported&code=faca0516-7160-4994-9765-1e4145b2d7ec
Timestamp: 2019-04-25 14:20:10+00:00

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The crucial step in the conversion of solar to chemical energy in photosynthesis takes place in the reaction centre, where the absorbed excitation energy is converted into a stable charge-separated state by ultrafast electron transfer events. However, the fundamental mechanism responsible for the near-unity quantum efficiency of this process is unknown. Here we elucidate the role of coherence in determining the efficiency of charge separation in the plant photosystem II reaction centre by comprehensively combining experiment (two-dimensional electronic spectroscopy) and theory (Redfield theory). We reveal the presence of electronic coherence between excitons as well as between exciton and charge-transfer states that we argue to be maintained by vibrational modes. Furthermore, we present evidence for the strong correlation between the degree of electronic coherence and efficient and ultrafast charge separation. We propose that this coherent mechanism will inspire the development of new energy technologies.
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We thank H. v. Roon for preparation of the PSII RC sample. E.R., M.F., J.T. and R.v.G. were supported by the VU University Amsterdam, the Laserlab-Europe Consortium, the TOP grant (700.58.305) from the Foundation of Chemical Sciences part of NWO and the advanced investigator grant (267333, PHOTPROT) from the European Research Council. E.R., M.F. and R.v.G. were supported by the EU FP7 project PAPETS (GA 323901). R.v.G. gratefully acknowledges his ‘Academy Professor’ grant from the Royal Netherlands Academy of Arts and Sciences (KNAW). V.I.N. was supported by the Russian Foundation for Basic Research (grant No. 12-04-01085) and by a NWO visitor grant. Work in the laboratory of D.Z. was supported by the Swedish Research Council, Knut and Alice Wallenberg Foundation and Wenner-Gren Foundations.
Present address: Center for Physical Sciences and Technology, LT-02300 Vilnius, Lithuania.
Present address: TU Delft, Applied Sciences ChemE/Chemical Engineering, 2600 GA Delft, The Netherlands.
E.R., R.A., M.F., J.T. and D.Z. collected the experimental 2DES data. R.A. and M.F. developed the data analysis programs. E.R. analysed the experimental data. V.I.N., E.R. and R.v.G. developed the theoretical modelling. E.R. D.Z. and R.v.G. designed the research. E.R., V.I.N., D.Z. and R.v.G. wrote the paper. All authors discussed the results and commented on the manuscript.

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