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The selective excitation of different modes and the detection of the effect of substituents on coupling and energy transfer via CARS spectroscopy were carried out using benzene derivatives.

Energy transfer is an important phenomenon of physicochemical systems vibrationally coupled to an environmental bath. For a condensed system, energy exchange from one mode to another is the first step of chemical reactions. In this work, we use femtosecond time-and frequency-resolved coherent anti-Stokes Raman scattering (CARS) spectroscopy technique to track molecular dynamics and energy transfer in pure aniline and its mixed solutions. In pure aniline, oscillatory structures in time-and frequency-resolved CARS spectra indicate that vibrational modes participate in the vibrational coupling, and the vibrational coupling process is necessary for energy transfer. In the Rh101 + /aniline mixed solution, vibrational dynamics and energy transfer processes are not detected due to strong hydrogen interactions. By comparing the experimental results for the pure aniline and the Rh101 + /anilinemixed solution, we find that energy transfer in the pure aniline depends mainly on the vibrational coupling; in the Rh101 + /aniline mixed solution, hydrogen bonds act as the molecular damper, which leads to a faster decay in the vibrational dynamics.