A new approach to the study of interfacial melting of ice: infrared spectroscopy

Abstract

Faraday observed in 1850 "that a particle of water which could retain the liquid state whilst touching ice on only one side, could not retain the liquid if it were touched by ice on both" (M. Faraday, Royal Institution Discourse, June 7, 1850; Experimental Researches in Chemistry and Physics (Taylor and Francis, New York, 1991)). Thus began the concept of interfacial melting, and the presence of a liquid water film on the surface of ice at temperatures of 0°C and below. Over the past few decades, there have been a number of measurements of interfacial melting. In some studies, the thickness of the thin film, variously called the quasi-liquid layer (QLL), liquid-like layer, surface melting layer, or premelting layer, has been determined. The results of these measurements demonstrate a striking variation depending on the experimental method and the nature of the ice samples. For example, at –0.1°C, the thickness values range over two orders of magnitude from around 1 to 100 nm. Although the disagreement can be partially explained by the differences in ice samples, the experimental techniques employed in measurements of the QLL thickness are based on different physical principals, and involve a web of assumptions for their deconvolution. We describe here the technique of infrared attenuated total reflection (ATR) spectroscopy that has been directed to the study of interfacial melting of ice for the first time. PACS No.: 83.50Lh