Non‐exponential dephasing of molecular vibrations in liquids, directly observed by ‘magic’ femtosecond CARS

Using ‘magic’ polarization geometries in time‐resolved coherent anti‐Stokes Raman spectroscopy, the isotropic (purely vibrational) scattering contribution was investigated. Non‐exponential dephasing was observed on the subpicosecond time‐scale, described in the Anderson‐Kubo formalism by the correlation time τ_c. Experimental data are reported for the neat liquids CH₂BrCl and (CH₃)₂SO in the CH stretching region. Values of τ_c = 330 fs and 240 fs, respectively indicate, homogeneous line broadening for the dephasing processes. The time‐domain data are supported by a novel analysis of spontaneous Raman data.