Low-power, low-field RYDMAR of the primary radical pair in photosynthesis

Abstract A low-power, low-field reaction yield detected magnetic resonance spectrometer is described. RYDMAR signals of photosynthetic reaction centres have been detected at microwave fields lower than 0.1 mT. It is concluded that the sum of the decay rate constants of the primary photoinduced radical pair is less than 0.42±0.02 ns −1 , and that the exchange interaction within the pair is between 0.1 and 1.0 mT.