Abstract
The dynamics of charge separation in the photosystem II reaction center (PSII-RC) in the presence of intramolecular vibrations with their frequency matching the energy gap between the exciton state acting as the primary electron donor and the first charge-transfer (CT) state are investigated. A reduced PSII-RC 4-state model explicitly including a CT state is analyzed within Redfield relaxation theory in the multidimensional exciton-vibrational (vibronic) basis. This model is used to study coherent energy/electron transfers and their spectral signatures obtained by two-dimensional electronic spectroscopy (2DES). Modeling of the time-resolved 2D frequency maps obtained by wavelet analysis reveals the origins of the coherences which produce the observed oscillating features in 2DES and allows comparing the lifetimes of the coherences. The results suggest faster excitonic decoherence as compared with longer-lived vibronic oscillations. The emerging picture of the dynamics unravels the role of resonant vibrations in sustaining the effective energy conversion in the PSII-RC. We demonstrate that the mixing of the exciton and CT states promoted by a resonant vibrational quantum allows faster penetration of excitation energy into the CT with subsequent dynamic localization at the bottom of the CT potential induced by the remaining non-resonant nuclear modes. The degree of vibration-assisted mixing and, correspondingly, the rate of primary charge separation, increases significantly in the case of electron-vibrational resonance. The observed features illustrate the principles of quantum design of the photosynthetic unit. These principles are connected with the phenomenon of coherent mixing within vibronic eigenstates, increasing the effectiveness of charge separation not only upon coherent and impulsive laser excitation utilized in the 2DES experiment, but also under natural conditions under non-coherent non-impulsive solar light illumination.
| Original language | English |
|---|---|
| Pages (from-to) | 5195-5208 |
| Number of pages | 14 |
| Journal | Physical Chemistry Chemical Physics - PCCP |
| Volume | 19 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - 21 Feb 2017 |
Funding
V. I. N. was supported by the Russian Foundation for Basic Research (Grant No. 15-04-02136); E. R. 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, the advanced investigator grant (267333, PHOTPROT) from the European Research Council, and the EU FP7 project PAPETS (GA 323901). R. v. G. gratefully acknowledges his Academy Professor grant from the Netherlands Royal Academy of Sciences (KNAW) and J. P. was supported by Ministerio de Economia y Competitividad Project No. FIS2015-69512-R and the Fundacion Seneca Project No. 19882/GERM/15.
| Funders | Funder number |
|---|---|
| EU FP7 | GA 323901 |
| Fundacion Seneca Project | 19882/GERM/15 |
| Koninklijke Nederlandse Akademie van Wetenschappen | |
| PHOTPROT | |
| Laserlab-Europe | 700.58.305 |
| European Research Council | |
| Koninklijke Nederlandse Akademie van Wetenschappen | |
| Vrije Universiteit Amsterdam | |
| Russian Foundation for Basic Research | 15-04-02136 |
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek | 267333 |
| Ministerio de Economía y Competitividad | FIS2015-69512-R |
