The Dynamics of Water in Heterogeneous Systems with Emphasis on Subzero Temperatures

Abstract

Water can exist in a variety of non-icelike forms at temperatures below 0°C when associated with ions, with other molecules, or with relatively rigid surfaces. The type of “structure” involving the water molecule and the observable dynamical properties of the water molecules depend to a certain extent upon the particular system being studied and upon its thermal, and possibly, mechanical history. At present, however, the situation is somewhat confused and no unifying pattern of behavior has been reported, indeed it is by no means certain that a uniform pattern of behavior will be observed over the full range of systems. The intention of this chapter is to review the dynamic properties of water at subzero temperatures for a range of systems, emphasis being placed on the molecular rather than the macroscopic properties. The chapter is arranged in order of increasing complexity, but with the objective of emphasizing the features that are common to many systems. By adopting this approach it will be found that the pursuit of a common theme will lead us relatively smoothly from one system to another. However, this has the unfortunate consequence that sectionalization becomes difficult and to a certain extent somewhat arbitrary. A further complication is that in the discussion it is necessary to describe particular experiments and in turn the techniques employed. Discussion of the techniques will be introduced as required, but the reader who is already familiar with the technique under discussion will be able to omit that particular section.