2011 Volume 80 Issue 10 Pages 894-897
In liquid water, water molecules form a disordered three-dimensional hydrogen bond network that continuously changes with time. The physical and chemical processes in liquid water are intimately connected with the microscopic dynamics of the hydrogen bond network, such as structural fluctuation and energy transfer. In this article, we present the ultrafast processes of such microscopic dynamics in liquid water, particularly the vibrational energy relaxation studied by mid-infrared nonlinear spectroscopy. The vibrational energy relaxation in liquid water is a phenomenon that determines thermalization and affects the chemical reactions in aqueous environments. It has been revealed that the energy relaxations of the intramolecular vibrational modes occur at the time scale of about 200 fs. In addition, the vibrational relaxation rates of these modes have been found to increase with decreasing temperature. This anomalous temperature dependence sheds light on the role of hydrogen bonds for rapid energy transfer.
