Fig. 1.

(Upper) Electron transfer between the donor and acceptor held at temperatures $T_R$ and $T_P$, respectively. (Lower) Arrhenius plot of the logarithm of the rate constant of electron transfer $\ln \left(k_{\text{ET}}\right)$ vs. $1/T$ for the equilibrium thermal bath with $T=T_R=T_P$ and for a nonequilibrium thermal bath, in which $T=T_R$ is varied and $T_P=280$ K is held fixed. The reaction is self-exchange electron transfer with zero reaction free energy and $E_{R1}=E_{R2}=0.5$ eV; $\text{ln}\left(k_{\text{ET}}\right)=-{\beta }_{\text{eff}}{F}^{†}$ is assumed for simplicity (the rate preexponential factor is put equal to unity).