The Mechanism and Kinetics of the O(1D) + Ethylene Reaction: Effects of a Submerged Peak Induced by van der Waals Interactions.

van der Waals (vdW) interactions are known to be important in chemical and biological processes, yet the understanding of their roles in polyatomic complex-forming reactions remains quite limited. In this work, we combine experimental and theoretical approaches to investigate the kinetics and mechanisms of the O-(1D)+C2H4 reaction. We find that vdW interactions between O-(1D) and ethylene cause a long-range submerged peak to form associated with a vdW well, decreasing the rate coefficients, altering their temperature dependence, and transforming the channel of O-(1D) attack on the H-C bond to a minor one. The underlying microscopic mechanism is revealed and is shown to differ significantly from the conventional insertion-type mechanism. The reaction channel involving O-(1D) addition to the CC bond is identified as dominant. The calculated rate coefficients are in very good agreement with experimental measurements. The product H atom yields are reported and elucidated. This work demonstrates that weak vdW interactions can be used to control chemical reactivity and reaction pathways, providing new insights into the kinetics and mechanisms of complex-forming reactions involving excited-state atoms.