Reaction Dynamics for the [NNO] System from State-Resolved and Coarse-Grained Models

TL;DR

This study investigates the reaction dynamics of NO and N atoms using state-resolved and coarse-grained models on different potential energy surfaces, revealing insights into reaction mechanisms, energy flow, and concentration profiles over time.

Contribution

It introduces a detailed comparison of state-resolved and Arrhenius-based models on high-level PESs, emphasizing the importance of non-equilibrium dynamics in reaction simulations.

Findings

Ignition points occur at ~10^{-6} s regardless of reverse rate assumptions.

Conversion from NO to N₂ is incomplete with Arrhenius rates but complete with STS.

Concentration profiles are consistent over 14 orders of magnitude in time using STS-based models.

Abstract

The dynamics for the NO($X^2 \Pi$) + N($^4$S) $\leftrightarrow$ N$_{2}(X^{1}\Sigma_{g}^{+}$) + O($^{3}$P) reaction was followed in the $^3$A' electronic state using state-to-state (STS) and Arrhenius-based rates from two different high-level potential energy surfaces represented as a reproducing kernel (RKHS) and permutationally invariant polynomials (PIPs). Despite the different number of bound states supported by the RKHS- and PIP-PESs the ignition points from STS and Arrhenius rates are at $\sim 10^{-6}$ s whether or not reverse rates are from assuming microreversibility or explicitly given. Conversion from NO to N$_2$ is incomplete if Arrhenius-rates are used but complete turnover is observed if STS-information is used. This is due to non-equilibrium energy flow and state dynamics which requires a state-based description. Including full dissociation leads asymptotically to the correct 2:1 [N]:[O] concentration with little differences for the species' dynamics depending on the PES used for the STS-information. In conclusion, concentration profiles from coarse-grained simulations are consistent over 14 orders of magnitude in time using STS-information based on two different high-level PESs.