A PECULIAR INTERFERENCE PHENOMENON OBSERVED IN FEMTOSECOND OPTICAL KERR-EFFECT SPECTROSCOPY FOR NEARLY TRANSPARENT MATERIALS

A sharp negative-going interference signal has been observed in femtos econd optically heterodyne-detected optical Kerr effect spectroscopy u sing a Ti:sapphire laser for excitation. This signal mainly appears in materials which have O-H bonds in their chemical structures and its w idth is narrower than the duration of the exciting pulse. Careful anal ysis shows that this phenomenon is connected with the weak light absor ption to vibrational overtones and is closely related to the spectral broadening of the exciting pulse through the transient grating created by pump and probe pulses. It is suggested that the lack of this inter ference effect in water may indicate the presence of a fast relaxation process.