Femotsecond dynamics of the hydrogen bond in water

A pump-probe experiment is described to study femtosecond dynamics of hydro gen bonds in liquid water. The key element of the experimental setup is a l aser source emitting 150 fs pulses in the 2.5-4.4 pm spectral region, at 10 mu J power level. The OH-stretching band is recorded for different excitat ion frequencies and different pump-probe delay times. Time-dependent solvat ochromic shifts are observed and are interpreted with the help of statistic al mechanics of nonlinear optical processes. Using these spectral data, the OH...O motions are "photographed" in real time.