Molecular diffusion in monolayer films of water adsorbed on a silica surface

Abstract

The dynamics of water adsorbed in near-monolayer films at the surface of silica has been measured and characterized by quasielastic neutron scattering. The analysis shows the coexistence of two phases of sorbed water molecules with different dynamics. One component is immobile on the experimental timescale, while the other has a two-dimensional diffusion coefficient of ca. 6 × 10^–10 m² s^–1 and a residence time during reorientation of 4 × 10^–12 s. The precise details of the reorientation process in the mobile phase are still unclear.