Two-dimensional electronic spectroscopy (2DES) is enabling new insight into the electronic structure, energy transfer pathways and charge separation mechanisms in photosynthetic systems. 2DES resolves the third order optical response as a function of both excitation and detection frequencies, offering a way to directly observe electronic coupling and map energy transfer between different states while separating homogeneous and inhomogeneous broadening. Here we use 2DES to obtain a comprehensive picture of the ultrafast processes from the initial photoexcitation to the formation of stable charge separated states in the bacterial reaction center (BRC) of <i>Rhodobacter sphaeroides</i> and the photosystem II reaction center (PSII RC) from spinach. We report 2DES measurements spanning the Qy bands of the RCs and present a global analysis of the kinetics of energy transfer and charge separation. At early times we also observe coherent dynamics in the RCs. We compare these to coherent dynamics in monomer pigments and discuss their possible functional relevance.<br/> <br/>

Probing ultrafast dynamics of photosynthetic reaction centers using two-dimensional electronic spectroscopy

253rd National Meeting (2017)

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