Revealing umbrella bending as a reporter mode in the D+CH<sub>4</sub> reaction.

Tan, Yuxin; Zhao, Bin; Yuan, Daofu; Li, Fan; Yu, Shanshan; Jin, Mengda; Zhang, Yu; Luo, Chang et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

How the non-reacting moiety of a molecule influences a polyatomic reaction has been a topic of much research interest. Here we present a comprehensive investigation of the D + CH<sub>4</sub> → HD + CH<sub>3</sub> reaction, a benchmark polyatomic elementary reaction with CH<sub>3</sub> as the non-reacting moiety, employing a high-resolution crossed molecular beams apparatus and an accurate seven-dimensional wave packet method. An interesting angular distribution of the CH<sub>3</sub>(v' = 1) product umbrella bending vibrational state is observed to scatter more in the sideways direction than the CH<sub>3</sub>(v' = 0) one. By monitoring the wave functions on a dividing surface in the transition state region, the CH<sub>3</sub> umbrella bending mode is established as a reporter mode that faithfully reveals how the D atom dynamically approaches CH<sub>4</sub> at different total angular momenta or impact parameters. This discovery of the reporter mode provides an opportunity for the detailed study of polyatomic reaction dynamics.