Dissection of the Multichannel Reaction O(3P) + C2H2: Differential Cross-Sections and Product Energy Distributions

Abstract

The O(3P) + C2H2 reaction plays an important role in hydrocarbon combustion. It has two primary competing channels: H + HCCO (ketenyl) and CO + CH2 (triplet methylene). To further understand the microscopic dynamic mechanism of this reaction, we report here a detailed quasi-classical trajectory study of the O(3P) + C2H2 reaction on the recently developed full-dimensional potential energy surface (PES). The entrance barrier TS1 is the rate-limiting barrier in the reaction. The translation of reactants can greatly promote reactivity, due to strong coupling with the reaction coordinate at TS1. The O(3P) + C2H2 reaction progress through a complex-forming mechanism, in which the intermediate HCCHO lives at least through the duration of a rotational period. The energy redistribution takes place during the creation of the long-lived high vibrationally (and rotationally) excited HCCHO in the reaction. The product energy partitioning of the two channels and CO vibrational distributions agree with experimental data, and the vibrational state distributions of all modes of products present a Boltzmann-like distribution.

Dynamics studies for the multi-well and multi-channel reaction of OH with C2H2 on a full-dimensional global potential energy surface

“…In the CO + CH 3 (P5) channel, product energy distributions are similar to that of the C 2 H 2 + O( 3 P) → CO + CH 2 reaction we had studied previously. 71 The relative translational energy and the CH 3 vibrational energy account for a relatively large fraction of the total available energy. The CO rotational state is highly excited, while the CO vibrational energy accounts for a small fraction, and the CO vibrational energy distribution is slightly characterized by a thermal equilibrium distribution.…”

Collaborative control of branching ratio in the O + HO2 → OH + O2 reaction via vibrational and rotational excitation

“…[ 5–13 ] The rapid progress of experimental and theoretical studies on the dynamics of multichannel reactions in recent years has greatly advanced our understanding of the dynamical control of reactivity and product branching. [ 14–16 ]…”

“…[5][6][7][8][9][10][11][12][13] The rapid progress of experimental and theoretical studies on the dynamics of multichannel reactions in recent years has greatly advanced our understanding of the dynamical control of reactivity and product branching. [14][15][16] However, most previous studies focused on reactions with only one reaction pathway, which cannot represent the general complex reactions with several pathways. Specifically, it is of great importance to understand what effect the different modes have on the branching ratio for competitive reaction pathways.…”