LOW-FREQUENCY MODES PROBED BY TIME-DOMAIN OPTICAL KERR-EFFECT SPECTROSCOPY

The principle and application of ultrafast optical Kerr effect (OKE) s pectroscopy have been reviewed. This spectroscopy is shown to be very useful to investigate low frequency modes in disordered materials and the obtained data are directly comparable with frequency-domain light scattering spectroscopy. Experimental study to show the consistency be tween the time- and frequency-domain spectroscopy has been performed f or liquid nitrobenzene and the excellent agreement is attained over th ree orders of magnitude in frequency range. It is also shown that the result obtained by the OKE measurement is consistent with that obtaine d by four wave mixing spectroscopy. Combination of these spectroscopic techniques is particularly suited for the investigation of low freque ncy modes because a wide frequency range is covered with great accurac y. Several remarks concerning the OKE spectroscopy are presented such as the breakdown of Debye relaxation model and various interference ef fects which may distort the time-domain data.