Abstract: 

Ice surfaces play important roles in atmospheric and interstellar chemistry promoting reactions affecting air quality in the polar boundary layer, upper tropospheric and stratospheric chemistry, and the formation of complex molecules in the interstellar medium.  We use molecular beam and surface science techniques, along with in situ optical/electronic spectroscopy/microscopy, to quantify the complex coupled interfacial kinetics for adsorption, desorption, diffusion and uptake of molecules by ice as well as those for phase separation and crystallization of the resulting mixed molecular solids.  A molecular-level interpretation of elementary heterogeneous (photo)chemical processes at the surface of ice is provided by molecular modeling and numerical simulations of simple model systems yielding insight into the rich ice surface physics and chemistry.  Result from studies of heterogeneous nitrates photochemistry and of confinement effects on the water nuclear spin isomers interconversion will be presented.