Presentation Information
[3G07]Vibrational ladder climbing in STM-based tip-enhanced sum frequency generation spectroscopy
*Tatsuto Mochizuki1,2, Shota Takahashi1, Atsunori Sakurai1,2, Toshiki Sugimoto1,2 (1. Institute for Molecular Science, 2. Graduate Institute for Advanced Studies, SOKENDAI)
Mode-selective vibrational excitation provides a promising approach for precise control of chemical reactions, but its application has been mostly limited to gas-phase systems. Achieving highly vibrationally excited states on metal surfaces has remained challenging due to fast vibrational relaxation processes. To address this, we focused on tip-enhanced sum frequency generation (SFG), which we have developed. This method enables the generation of an intense infrared field at the confined region, sufficient to drive vibrational excitation to higher levels. We detected tip-enhanced SFG spectra of CO adsorbed on Pt(111), where multiple peaks emerged under intense infrared excitation. These peaks are assigned to transitions between highly vibrationally excited states, indicating sequential vibrational excitation within a single pulse, known as "vibrational ladder climbing". This finding demonstrates the potential of tip-enhanced SFG for driving mode-selective chemistry on surfaces.