Near-zero-frequency stimulated Raman gain spectroscopy in CS(2).

We have obtained the low-frequency dispersion of Im X((3)) in CS(2) by stimulated Raman gain technique with a simple low-power cw-pulsed laser system. The theoretical relationship between the nonlinear spectrum and the spontaneous spectrum is confirmed. The unique capability of the technique for low-frequency Raman measurements is well demonstrated with the detection of a weak near-zero-frequency mode.