Application of the density matrix method to the primary electron transfer in photosynthetic reaction centers

The ultrafast time evolution of the primary electron transfer processes in photosynthetic reaction centers is theoretically studied by consideration of protein-induced and direct mechanisms in the density matrix method. The effective Liouvillian for the primary electron transfer processes in the pigment molecules is derived by projecting out the variables of the protein subunits. The protein-induced and direct electron transfer mechanisms are considered through the imaginary and real parts of the effective Liouvillian respectively. The model calculations of the population changes in the photosynthetic reaction center of Rhodopseudomonas viridis show that the protein-induced electron transfer mechanism plays an important role in the primary electron transfer processes. The model calculation is carried out without invoking the adiabatic approximation, i.e. stationary approximation of the off-diagonal density matrix elements.