Vibrational spectroscopy and modeling of the surface and subsurface of ice and of ice-adsorbate interactions

FT-IR spectroscopic results in conjunction with simulations show that ice nanocrystals, formed at 70 K and annealed at 140 K, consist of a crystalline core, a highly irregular (though relatively smooth) crystalline surface, and a slightly distorted subsurface region connecting the surface and bulklike interior ice. Adsorbates on the nanocrystalline surface can be divided into three classes in terms of their effect on the three regions of the nanocrystals: weak adsorbates that influence the surface only; strong adsorbates that reverse the restructuring of the ice surface and thereby increase the order of the subsurface region; penetrating strong adsorbates that completely convert the nanocrystals to hydrates at cryogenic temperatures. To the extent that these properties of crystalline nanoparticles reflect the characteristics of the surface region of bulk ice, they must be recognized in attempts to understand chemistry at the ice surface.