  We present a state-space-based path integral method to calculate the rate of
electron transfer (ET) in multi-state, multi-electron condensed-phase
processes. We employ an exact path integral in discrete electronic states and
continuous Cartesian nuclear variables to obtain a transition state theory
(TST) estimate to the rate. A dynamic recrossing correction to the TST rate is
then obtained from real-time dynamics simulations using mean field ring polymer
molecular dynamics. We employ two different reaction coordinates in our
simulations and show that, despite the use of mean field dynamics, the use of
an accurate dividing surface to compute TST rates allows us to achieve
remarkable agreement with Fermi's golden rule rates for nonadiabatic ET in the
normal regime of Marcus theory. Further, we show that using a reaction
coordinate based on electronic state populations allows us to capture the
turnover in rates for ET in the Marcus inverted regime.
