Covalent and ionic stales of strong acids at the ice surface

The relationship between the degree of ionization and the environment of a strong acid is of basic scientific interest. Often this relationship reduce s to the interdependence of ion/acid hydration and proton transfer. Despite the presence of pure water, the surface of crystalline ice, particularly a t cryogenic temperatures, is one of limited (controlled?) availability of w ater of hydration. Here, the detailed nature of the ice surface and the sta tes of strong acids adsorbed to ice at cryogenic temperatures are examined. These subjects are of special current interest since the ability to model the complex chemistry that occurs on the surfaces of water-rich particles i n the atmosphere, particularly in the stratosphere over the polar regions, requires a valid concept of the acid-ice interface. Our combined spectrosco pic and simulation studies have identified the surface of fret-standing ice particles as badly disordered, with a range of water-ring sizes and an inc reased level of H-bond saturation relative to an ordered ice surface. FT-IR results are reported for the interaction of the surface of such ice partic les with submonolayer amounts of adsorbed DCl, DBr, and HNO3 and for multil ayer exposure to DCl. The DCl and DBI adsorbed states demonstrate behavior familiar from observations on strongly bound molecular adsorbates. Two meth ods have been devised for exposure of the nanocrystals to HNO3. One gives a n ionic state initially, while the initial state of the other approach is m olecular. In both instances, the system is observed to evolve, with time/wa rming, towards a common mixed molecular-ionic adsorbed state.