Competition between trapping and annihilation in photosystem I
The study of exciton transfer and primary charge separation in photosynthesis requires excitation by picosecond flashes. If a significant fraction of the reaction centers (RCs) shall be closed by a flash, the excitation density must be chosen such high that more than one exciton resides at the same time in the pool of antenna pigments. Then excitons can be lost by singlet-singlet annihilation before they are trapped by the photochemistry in the RC. Annihilation leads to an apparent acceleration of all other reactions connected with the exciton dynamics. The quantitative treatment of this competitive deactivation path allows the bimolecular rate constant of exciton-exciton annihilation to be determined that characterizes a given antenna bed.
KeywordsPurple Membrane Trapping Time Primary Charge Separation Bimolecular Rate Constant Antenna Pigment
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