Abstract

New nonlinear methods sensitive to surface vibrational dynamics are presented. Femtosecond vibrational sum frequency generation allows for time-and frequency-domain vibrational spectroscopies and shows coherent nuclear motion (surface quantum beats) which dephases on a timescale dependent on surface inhomogeneity. A two-beam, equal pulse correlation technique has been used to examine low frequency intramolecular and intermolecular motions of organic molecules at the fused silica/air interface. The time-resolved parametric signals are modulated by adsorbate vibrational motion driven through stimulated Raman excitation. Frequency analysis of the temporal response of p-chloroaniline shows strong contributions at 80 and 120 cm⁻¹, consistent with the excitation of low frequency Raman active lattice modes of crystalline p-chloroaniline.

© 2002 Optical Society of America