The product minimum is closer to the PC vector, but a substantial movement along the ET dimension is needed to reach this minimum as well as the transition state; the coordinates of these points in the basis of ⃗ p and ⃗ q are listed in Table . Though the exact reaction pathway is unknown, we propose that it will lie in a trapezoidal region between the two minima, bounded by ⃗ p and ⃗ q. Only one minimum is found in the ET excited state (Figure ), and it is located above the transition state of the ground state PES. Presence of no additional minima in the excited state suggests that the chargeseparated states are not stable for the phenol/phenoxy pair. The small energy gap of 0.11 eV between the ground and excited states at the position of the tran- sition state (see Table ) indicates a weakly coupled system and a PCET proceeding in the non-adiabatic regime.