Coherent coupling between vibrational modes of C-H bonds at different positions studied by femtosecond time-resolved coherent anti-Stokes Raman scattering

We performed femtosecond time-resolved coherent anti-Stokes Raman scattering(fs-CARS) measurements on liquid toluene and PVK film.For both samples,we selectively excited the CH stretching vibrational modes and observed the expected quantum beat signals.The frequency of the well-defined beats is in good agreement with the energy difference between the two simultaneously excited modes,which demonstrates that a coherent coupling between the vibrational modes of the C-H chemical bonds exists at the different positions of the molecules.The dephasing times of the excited modes are obtained simultaneously.