Phase state of water adsorbed on ice nucleating particles

Barnes and Sänger (1961) suggested that a substance only becomes active at nucleating ice when the adsorbed water on the surface is in an ice-like state, and that there should be a correspondence between the temperature of ice nucleation and the “freezing” of adsorbed water. We present spectroscopic measurements that allow to simultaneously determine the amount of adsorbed water and whether the adsorbed water is liquid or ice-like. These measurements are conducted using a new setup that allows to expose test substances to a broad temperature and humidity range while recording the diffuse infrared reflectance spectrum of the adsorbed water. The phase state of the adsorbed water with decreasing temperature is then compared to the ice nucleation temperature of the test substance, which is measured using a continuous flow diffusion chamber. References: Barnes, G. T., and Sänger, R., ZAMP 12, 159 (1961).