Fig. 8. The ESIPT of 3-HTCA in the SN1 and SNn states. The 3D plot contains the proton transfer coordinate and solvent polarization coordinate. The latter is where the solvent induced barrier is introduced during ESIPT in the lowest lying states. This is due to different equilibrium polarization between SN1 and ST1, which is presented by its coupling with the solvent polarity induced barrier along the solvent polarization coordinate.
