Atomic and Molecular Collisions at Liquid Surfaces

The gas-liquid interface remains one of the least explored, but nevertheless most practically important, environments in which molecular collisions take place. These molecular-level processes underlie many bulk phenomena of fundamental and applied interest, spanning evaporation, respiration, multiphase catalysis, and atmospheric chemistry. We review here the research that has, during the past decade or so, been unraveling the molecular-level mechanisms of inelastic and reactive collisions at the gas-liquid interface. Armed with the knowledge that such collisions with the outer layers of the interfacial region can be unambiguously distinguished, we show that the scattering of gas-phase projectiles is a promising new tool for the interrogation of liquid surfaces with extreme surface sensitivity. Especially for reactive scattering, this method also offers absolute chemical selectivity for the groups that react to produce a specific observed product.