Enlarging the reactive cone of acceptance by exciting the C–H bond in the O(3P) + CHD3 reaction

Abstract

The effects of the CH stretching vibration of methane on the O(³P) + CHD₃ reaction are elucidated in a crossed-beam imaging experiment. For the H-atom abstraction channel, the ground state reaction leads mainly to the vibrational ground states of products, OH(v = 0) + CD₃(v = 0). When the reactant CHD₃ is prepared with one-quantum excitation of CH stretching vibration (v₁ = 1), more than 90% of OH coproducts that formed concomitantly with the CD₃(v = 0) product are in v = 1. Significant vibrational enhancement in the reaction rate is observed, and the product angular distribution shifts from a backward-dominance in O(³P) + CHD₃(v = 0) to a sideways-peaking upon CH stretching excitation. As to the D-atom abstraction channel, the C–H bond excitation, despite being conserved in the CHD₂ product, unexpectedly hinders the overall reactivity of the unexcited C–D bond. We interpret the experimental findings as the result of enlarging the reactive cone of acceptance in abstracting the H atom at the expense of the cone for the D-atom transfer channel.