Quantum and Quasi-classical Dynamics of the C($^{3}$P) + O$_{2}$($^3\Sigma_{g}^{-}$) $\rightarrow$ CO($^{1}\Sigma^{+}$)+ O($^{1}$D) Reaction on Its Electronic Ground State

TL;DR

This study compares quantum and quasi-classical methods to analyze the ground-state dynamics of the C + O2 reaction, revealing good agreement at low energies and providing insights into reaction probabilities and product state distributions.

Contribution

It demonstrates that quasi-classical trajectory simulations effectively replicate quantum results for the C + O2 reaction at low energies, offering a computationally efficient alternative.

Findings

Quantum and QCT methods agree well at low collision energies.

Reaction probabilities show undulations linked to CO2 intermediate stabilization.

QCT accurately predicts vibrational and rotational product distributions at low energies.

Abstract

The dynamics of the C($^{3}$P) + O$_{2}$($^3\Sigma_{g}^{-}$) $\rightarrow$ CO($^{1}\Sigma^{+}$)+ O($^{1}$D) reaction on its electronic ground state is investigated by using time-dependent wave packet propagation (TDWP) and quasi-classical trajectory (QCT) simulations. For the moderate collision energies considered ($E_{\rm c} = 0.001$ to 0.4 eV, corresponding to a range from 10 K to 4600 K) the total reaction probabilities from the two different treatments of the nuclear dynamics agree very favourably. The undulations present in $P(E)$ from the quantum mechanical treatment can be related to stabilization of the intermediate CO$_2$ complex with lifetimes of on the 0.05 ps time scale. This is also confirmed from direct analysis of the QCT trajectories. Product diatom vibrational and rotational level resolved state-to-state reaction probabilities from TDWP and QCT simulations also agree well except for the highest product vibrational states $(v' \geq 15)$ and for the lowest product rotational states $(j' \leq 10)$. Opening of the product vibrational level CO$(v' = 17)$ requires $\sim 0.2$ eV from QCT and TDWP simulations with O$_2$($j=0$) and decreases to 0.04 eV if all initial rotational states are included in the QCT analysis, compared with $E_{\rm c} > 0.04$ eV obtained from experiments. It is thus concluded that QCT simulations are suitable for investigating and realistically describe the C($^{3}$P) + O$_{2}$($^3\Sigma_{g}^{-}$) $\rightarrow$ CO($^{1}\Sigma^{+}$)+ O($^{1}$D) reaction down to low collision energies when compared with results from a quantum mechanical treatment using TDWPs.