Mechanism of primary charge separation in impulse-driven photosynthetic experiments

Determine the precise mechanism of charge separation in impulse-driven experiments on photosynthetic reaction centres, including whether a low-frequency vibrational mode drives an exciton pair into a charge-separated state through resonance.

Background

The paper situates its spectroscopy of deprotonated chlorophyll pigments within the broader effort to understand primary charge separation in photosynthetic reaction centres. Although experimental studies have identified several steps in the reaction scheme, the precise mechanism governing charge separation in impulse-driven experiments remains unresolved. The authors mention a proposed mechanism in which a low-frequency vibrational mode promotes an exciton pair into a charge-separated state through resonance, but they do not establish whether this mechanism is correct.

The unresolved mechanism motivates the search for detailed vibrational and electronic spectroscopic information on chlorophyll pigments, including low-frequency modes that could participate in charge-transfer dynamics. The measurements reported in the paper characterize such modes in isolated deprotonated pheophorbide anions, but do not resolve the underlying charge-separation mechanism in reaction centres.