Reactive scattering of ground-state and electronically excited oxygen atoms on a liquid hydrocarbon surface

We have directed a supersonic beam of atomic oxygen containing a large concentration of ground-state O( 3P) and a small percentage of electronically excited O( 1D) at a continuously refreshed liquid film of a long-chain saturated hydrocarbon, squalane (C 30H 62). Angularly resolved flux and energy distributions of reactively scattered products revealed that the dominant volatile reaction product is the OH radical, which can be formed by an Eley-Rideal direct-reaction mechanism or by a process that leads to trapping and desorption of the initial product. Both of these processes occur with comparable probabilities. A second product, H 2O, is thought to be formed by abstraction of a hydrogen atom from the hydrocarbon chain by the primary OH product. The H 2O product also exits the surface via non-thermal and thermal mechanisms, although the thermal mechanism dominates.