On Electron Spin Polarization Created in the Excited Triplet State of Accesory Chlolophyll via Photoinduced Charge-Recombination of the Photosystem II Reaction Center

We present a theoretical approach to investigate the electron spin polarization (ESP) of the excited triplet state that has been detected by using the time-resolved EPR (TREPR) method in the Photosystem II reaction center (PS II RC) of the plants. We show, by using the stochastic-Liouville equation, that the ESP pattern created in the accessory chlorophyll (ChlaccD1) which reside near the PD1 chlorophyll of the active branch is explained by one-step, concerted double electron transfer model initiating from the singlet-triplet conversion of the light-induced charge-separated (CS) state composed of PD1 radical cation and pheophytin radical anion. We also considered the sequential electron spin polarization transfer (ESPT) model via 1) the triplet charge-recombination (CR) and 2) the triplet-triplet energy transfer processes. It has been clearly shown that the ESP created in the ChlaccD1* is dependent on the rate constant (kTT) of the triplet-triplet energy transfer from the