Selective
excitation of C–H stretching vibrational modes,
detection of intramolecular vibrational energy redistribution (IVR),
and vibrational modes coupling in the electronic ground state of benzene
are performed by using femtosecond time- and frequency-resolved coherent
anti-Stokes Raman scattering (CARS) spectroscopy. Both of the parent
modes in the Raman-active bands are coherently excited by an ultrafast
stimulated Raman pump, giving initial excitations of 3056 cm–1 (A1g) and 3074 cm–1 (E2g) and subsequent IVR from the parent modes to daughter modes of 1181
and 992 cm–1, and the coherent vibrational coupling
of the relevant modes is tracked. The directionality and selectivity
of IVR and coherent coupling among all of the relevant vibrational
modes are discussed in the view of molecular symmetry.