Studies of Thin Film Water

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George Ewing of Indiana University is supported by the Experimental Physical Chemistry Program to carry out research that aims to quantify the unique thermodynamic properties of thin film water on model insulator surfaces, principally by infrared spectroscopy. These properties include free energy, enthalpy and entropy values, freezing points (if indeed films do freeze), and phase relationships in the formation of gas clathrate hydrates within the films. In addition, spectroscopic studies, together with theoretical collaborations, are expected to yield structural information on molecular orientations and hydrogen bonding networks from submonolayer to multilayer adlayers of water. The model insulator surfaces will include those associated with ionic (such as magnesium oxide), covalent (such as silica), and molecular (such as polyethylene) substrates. Ice near its melting point will receive particularly close attention as a substrate. Surface melting studies of ice induced by gaseous sulfur dioxide and formation of the sulfur dioxide-clathrate at the ice-vapor interface could improve understanding of the nature of anomalous sulfur dioxide uptake by snow in the Earth's polar regions. Thin films of water coat many common substances in the natural environment, including ice near its melting point. Like other nanostructures, thin films of water exhibit behavior that is different from that of bulk liquid water. This research will explore significant properties of these ubiquitous films. Outcomes are expected to impact fundamental issues in the properties of thin water films, and will be relevant to many problems in environmental science. Examples of applications where thin water films play an important role are in cloud formation, soil properties, and caking problems in solids (such as salt, detergents, and fertilizer).