Non-thermal Vibrational Activation of Reactants in Plasmon Assisted Chemical Reactions

Recent studies on plasmon assisted chemical reactions postulate that the hot-carriers of plasmon-excited nanostructures may induce a non-thermal vibrational activation of metal-bound reactants. However, a quantitatively validation at the level of molecular quantum states is currently missing. In this talk, I will present our recent spectroscopic studies on metal-bound reactants, which proves the non-thermal vibrational molecular excitations caused by plasmons: We find that such a plasmon- induced vibrational excitation causes hyper-thermal vibrational population distribution of a specific molecular vibrational mode, and bring significant population in overtone-excited states. Such excitation is found to be critically dependent on the metal-molecule chemical contact. The inelastic molecule-electron scattering model could fully explain what are observed. The result not only provides the physical basis for the plasmon-assisted chemical reactions, but also pave the way for controlling chemical reactions on metal surfaces.