FEMTOSECOND OPTICAL KERR-EFFECT STUDIES OF WATER

The time-resolved optical Kerr effect of water at 298 K was investigat ed using pulse widths (full width at half-maximum) as short as 38 fs t o characterize the dynamic response of water from tens of femtoseconds to several picosecond time scales. A frequency analysis of the free i nduction decay of the excited Raman modes observed maxima at 40 and 16 5 cm(-1), with a broad distribution of higher frequency components cen tered around 470 cm(-1). There is an initial rapid decay in the induce d birefringence of less than 50 fs due to interference between these m odes. These features are id good agreement with previous depolarized l ight scattering studies. Additional relaxation components of 500 +/- 3 0 fs and 1.7 +/- 0.3 ps are resolved in the Kerr results. In total, th ese observations depict an overall dynamic pathway for the relaxation of water.