  We present a detailed analysis of the mechanism of the primary charge
separation process in bacterial photosynthesis using real-time path integrals.
Direct computer simulations as well as an approximate analytical theory have
been employed to map out the dynamics of the charge separation process in many
regions of the parameter space relevant to bacterial photosynthesis. Two
distinct parameter regions, one characteristic of sequential transfer and the
other characteristic of superexchange, have been found to yield charge
separation dynamics in agreement with experiments. Nonadiabatic theory provides
accurate rate estimates for low-lying and very high-lying bacteriochlorophyll
state energies, but it breaks down in between these two regimes.
