Dynamics of interfacial reactions between O(3P) atoms and long-chain liquid hydrocarbons

Recent progress that has been made towards understanding the dynamics of collisions at the gas-liquid interface is summarized briefly. We describe in this context a promising new approach to the experimental study of gas-liquid interfacial reactions that we have introduced. This is based on laser-photolytic production of reactive gas-phase atoms above the liquid surface and laser-spectroscopic probing of the resulting nascent products. This technique is illustrated for reaction of O(P-3) atoms at the surface of the long-chain liquid hydrocarbon squalane ( 2,6,10,15,19,23-hexamethyltetracosane). Laser-induced fluorescence detection of the nascent OH has revealed mechanistically diagnostic correlations between its internal and translational energy distributions. Vibrationally excited OH molecules are able to escape the surface. At least two contributions to the product rotational distributions are identified, confirming and extending previous hypotheses of the participation of both direct and trapping-desorption mechanisms. We speculate briefly on future experimental and theoretical developments that might be necessary to address the many currently unanswered mechanistic questions for this, and other, classes of gas-liquid interfacial reaction.