Nonresonant vibrational energy transfer on metal nanoparticle/liquid interface

Knowledge of vibrational energy transfer on a metal nanoparticle/liquid interface is essential for understanding the energy conversion process involved in many heterogeneous nanocatalyses. In this study, we investigate mode-specific vibrational energy transfer between CO molecules on different adsorbate sites on a 1 nm platinum metal nanoparticle/liquid interface by using ultrafast two-dimensional IR spectroscopy. The vibrational energy transport is found to be induced by vibration/vibration coupling with very little surface electron/vibration mediation. The energy transfer rate is determined to be about 1/140 ps^-1 from the atop site CO to the bridge site CO, and the specific rate is around 1/400 ps^-1 between the two nearest adsorbates. The energy transfer between different adsorbate sites can be described by the dephasing mechanism reasonably well. The mechanical coupling may contribute to the transfer, but analyses suggest that the role of dipole/dipole interaction is a more important factor for the energy transfer.