Coherent Vibrational Dynamics and High-resolution Nonlinear Spectroscopy: A Comparison with the Air/DMSO Liquid Interface

We present a comparative study on the C-H stretching vibrations at air/DMSO (dimethyl sulfoxide) interface with both the free-induction decay (FID) coherent vibrational dynamics and the sub-wavenumber high resolution sum-frequency generation vibrational spectroscopy measurements. In principle the frequency-domain and time-domain spectroscopic measure-ments should generate identical information for a given molecular system. However, when the molecular systems are with several coupled or overlapping vibrational modes, obtain-ing detailed spectroscopic and coherent dynamics information is not as straightforward and rather difficult from either the time-domain or the frequency domain measurements. For the case of air/DMSO interface that is with moderately complex vibrational spectra, we show that the frequency-domain measurement with sub-wavenumber high-resolution sum-frequency generation vibrational spectroscopy is probably more advantageous than the time-domain measurement in obtaining quantitative understanding of the structure and coherent dynamics of the molecular interface