Far-Infrared Studies on the Intermolecular Dynamics of Systems Containing Water. The Influence of Ionic Interactions in NaCl, LiCl, and HCl Solutions

摘要

We report, for the first time, extended very far IR (VFIR) intensity data (2.5-30 cm~(-1)) for solutions of NaCl, LiCl, and HCl in water over the accessible concentration (0-10 M) and temperature ranges (-100 deg to 80 deg C). This allows dynamic processes in the 0.2-2.0 ps regime to be probed, a suitable choice in view of much experimental data which shows that dynamic processes in this regime are important in liquid water. We have interpreted the data be consideration of (a) conductivity processes, shown only to be important at lowest frequencies, (b) changes in the rotational and translational dynamics of the water molecules, (c) M~+H_2O rattling modes, and (d) modifications of the water network "structure" and collective dynamics for different ions. The changes in intensity with concentration and temperature have been shown to be consistent with the expected changes of the ion-containing water network for different ion types.