Femtosecond CARS on H2

Time-resolved non-resonant CARS (coherent anti-Stokes Raman spectroscopy) is applied to probe H2 in the gas phase with femtosecond time resolution. The experimental transients show detailed beating structures, reflecting the rotational dynamics of all thermally populated ground state J levels with high fidelity. Modelling of the experimental data yields temperatures and pressures with high resolution. The good agreement with values determined by frequency-domain experiments demonstrates the suitability of this method for the determination of J-dependent collisional-broadening and line-shifting coefficients in gaseous mixtures at high pressures and temperatures, where frequency-domain CARS spectra are difficult to model.