Determination of Excited-State Energies and Dynamics in the B Band of the Bacterial Reaction Center with 2D Electronic Spectroscopy
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- 作者：Gabriela S. Schlau-Cohen ; Eleonora De Re ; Richard J. Cogdell ; Graham R. Fleming
- 刊名：The Journal of Physical Chemistry Letters
- 出版年：2012
- 出版时间：September 6, 2012
- 年：2012
- 卷：3
- 期：17
- 页码：2487-2492
- 全文大小：303K
- 年卷期：v.3,no.17(September 6, 2012)
- ISSN：1948-7185
文摘
Photosynthetic organisms convert photoenergy to chemical energy with near-unity quantum efficiency. This occurs through charge transfer in the reaction center, which consists of two branches of pigments. In bacteria, both branches are energy-transfer pathways, but only one is also an electron transfer pathway. One barrier to a full understanding of the asymmetry is that the two branches contain excited states close in energy that produce overlapping spectroscopic peaks. We apply polarization-dependent, 2D electronic spectroscopy to the B band of the oxidized bacterial reaction center. The spectra reveal two previously unresolved peaks, corresponding to excited states localized on each of the two branches. Furthermore, a previously unknown interaction between these two states is observed on a time scale of 100 fs. This may indicate an alternative pathway to electron transfer for the oxidized reaction center and thus may be a mechanism to prevent energy from becoming trapped in local minima.