The Dynamics and Kinetics of Water Interactions with a Condensed Nopinone Surface

Water and organic molecules are omnipresent in the environment, and their interactions are of central importance in many Earth system processes. Here we investigate molecular-level interactions between water and a nopinone surface using an environmental molecular beam (EMB) technique. Nopinone is a major reaction product formed during oxidation of β-pinene, a prominent compound emitted by coniferous trees, which has been found in both the gas and particle phases of atmospheric aerosol. The EMB method enables detailed studies of the dynamics and kinetics of D2O molecules interacting with a solid nopinone surface at 202 K. Hyperthermal collisions between water and nopinone result in efficient trapping of water molecules, with a small fraction that scatter inelastically after losing 60–80% of their incident kinetic energy. While the majority of the trapped molecules rapidly desorb with a time constant τ less than 10 μs, a substantial fraction (0.32 ± 0.09) form strong bonds with the nopinone surface and rema...