Intermolecular vibrational energy exchange directly probed with ultrafast two dimensional infrared spectroscopy.

Ultrafast two dimensional infrared (2D IR) spectroscopy has been applied to probe the intermolecular vibrational energy exchange between two model molecules, benzonitrile and acetonitrile-(d3). The vibrational energy exchange between these two molecules is manifested through the growth of cross peaks in their 2D IR spectra. In experiments, their nitrile groups (CN) are not involved in the energy exchange but serve as reporters of the process. Our experiments demonstrate that intermolecular vibrational energy transfer can be directly probed with the 2D IR method. Results also show that the mode specific energy transfer can be important in intermolecular vibrational energy transfers.