Corresponding to the collision energy of 7.8 kcal/mol, the reaction between O(3P) and dimethylamine leads to two product channels, namely, (1) ²OH and ²CH₃NHCH₂ (major product) and (2) ²OH and ²CH₃NCH₃ (minor product). Both pathways follow direct and indirect H abstraction mechanisms.

Abstract

In order to provide atomistic details for the mechanism of the collisional dynamics of O(³P) and dimethylamine (DMA) in the triplet electronic surface, direct dynamics simulations are reported herein. The simulations are performed at the U-HSE06/aug-cc-pVDZ level of theory. The results are reported for the relative collision energy of 7.8 kcal/mol. For the vibrational and rotational excitations, following temperature regimes have been considered: 200 and 10 K, respectively. Simulations reveal that the reaction can lead to two product channels in the considered energy regime: (1) ²OH + ²CH₃NHCH₂ and (2) ²OH + ²CH₃NCH₃. The computed reaction cross section for pathways 1 and 2 are as follows: 17.89  ± 0.20 Ų and 3.28  ± 0.03 Ų, whereas the computed microcanonical reaction rate constants for pathways 1 and 2 are as follows: (4.21  ± 0.05)*10⁻¹⁰ and (7.72  ± 0.07)*10⁻¹¹ cm³/(molecule sec). Both pathways follow direct and indirect H abstraction processes. Among the direct pathways, stripping and rebound mechanisms have been observed, whereas the indirect pathway involves formation of a post-reaction complex having lifetime ~0.4–0.5 ps. The velocity scattering angle distribution for the reaction is dominated by scattering in the sideways (60–120 °) and backward (120–180 °) directions with some contribution from the scattering in the forward direction (0–60 °).