Real-time observation of the singlet–triplet dephasing effect on the spin dynamics of the spin-correlated radical pair formed in the photolysis of tetraphenylhydrazine in a micelle

The effect of the singlet–triplet (S–T) dephasing caused by the modulation of the exchange interaction is discussed on the basis of the time-resolved ESR spectra of the singlet-born radical pair formed in the photolysis of tetraphenylhydrazine in an SDS (sodium dodecyl sulfate) micelle. The time evolution of the spectrum is simulated by the calculation with the Liouville equation. By comparison of the experimental results with the calculation, we estimated the rate constant of the S–T dephasing to be 2×107 s−1. The relation between the population relaxation due to the S–T dephasing and the relative magnitude of the exchange interaction and the S–T0 mixing is also discussed.