Vibrational dynamics of nitromethane mixed with IR780 dye studied by coherent anti-stokes Raman spectroscopy

Abstract

Vibrational coupling between different kinds of molecules in liquid mixture is studied by multiplex coherent anti-Stokes Raman spectroscopy (CARS). To identify vibrational coherence, fs-probe with high time resolution and narrowband-probe with high spectral resolution are adopted in CARS experiments. Using liquid nitromethane (NM) mixed with organic dye IR780 perchlorate as the sample, we can clearly observe the interference between different vibrational modes. The intermolecular vibrational interaction between NM and IR780 molecules results in the vibrational coherence transfer (VCT) in the form of a change of phase correlation. Compared with symmetric bending vibration of NO2, coherence transfer is found to be easier to take place between C―N bond of NM and vibrations of IR780, which indicates the selectivity of intermolecular vibrational interaction. The selectivity is deduced to be related to the coordination between intramolecular and collective motion of molecules. Copyright © 2016 John Wiley & Sons, Ltd.