Motion of hydrogen bonds in diluted [Formula Presented] solutions: Direct probing with 150 fs resolution

An experiment is described to study temporal variations of the hydrogen bond length in diluted [Formula Presented] solutions. The principles of this laser spectroscopic experiment are explained first. The construction of a laser source generating [Formula Presented] pulses in the [Formula Presented] spectral region at a [Formula Presented] power level is detailed next. The OH stretching band is reproduced for different excitation frequencies and different pump-probe delay times. A theory, based on statistical mechanics of nonlinear optical processes, is proposed to calculate the lowest two spectral moments. An effect is reported, the delay dependent vibrational solvatochromism. It is shown how this effect can be exploited to follow temporal variations of the [Formula Presented] bond length directly, in real time. The corresponding time scales are of the order of [Formula Presented] No bond oscillations are observed.