Fig3. Schematic diagram for the 2PP excitation at the CH3OH/TiO2 interface. The photoinduced charge transfer from the partially reduced Ti5c-δ sites (N0) to the CH3OH overlayer (N1) initiates the coupled electron-nuclear dynamics. The redistribution of charge elicits a dielectric response involving fast Ti–O bond stretching (polaron formation) along with slower adsorbate reorganization (solvation) to relax the initially prepared N1 to a quasi-stable N1* state. Simultaneously, the population decay by reverse charge transfer evolves from the nonadiabatic (τna) to the proton-coupled (τPCET) regimes.