Relation between the OH stretching frequency and the OO distance in time-resolved infrared spectroscopy of hydrogen bonding

Abstract A non-empirical theory is presented to study the relation between the OH stretching frequency and the OO distance in ultrafast laser spectra of water. Diluted solutions HDO / D 2 O rather than pure H 2 O were considered to switch off resonant vibrational interactions between water molecules; the local structure of water as well as the OO distribution functions remain unchanged in this substitution. Only times superior to 100 – 200 fs are considered to avoid perturbations generated by collisions between water molecules. It is then shown that the Novak–Mikenda type relations between the OH stretching frequency and the OO distance largely survive when going from equilibrium to laser perturbed non-equilibrium systems. It is also shown that temporally varying infrared pump–probe profiles of OH stretching bands in HDO / D 2 O closely parallel the oxygen–oxygen distribution functions of these solutions. Infrared pump–probe spectroscopy can thus replace time-resolved X-ray diffraction in this particular case.