Towards Quantitative Reaction Dynamics of O3

TL;DR

This study models the reaction dynamics of O(3P) with O2 to understand rate behaviors and isotope effects, revealing quantum effects' importance and improving rate predictions over previous models.

Contribution

It provides a high-level quantum chemical potential energy surface for O3 reactions and analyzes isotope effects and quantum influences on reaction rates.

Findings

Negative temperature dependence of reaction rates matches experiments.

Quantum effects, especially zero-point energy, significantly influence reaction rates.

Improved rate estimates over previous models, with some underestimation noted.

Abstract

The reaction dynamics of O(3P) + O2(3Sigma_g-) collisions in the O3(1A') electronic ground state is characterized on a high-level MRCI+Q/aug-cc-pVQZ potential energy surface represented as a reproducing kernel. For the atom exchange reactions involving the ^{16}O and ^{18}O isotopes as the atomic collision partner, associated with rates k6(T) and k8(T), respectively, a negative temperature-dependence of k(T), consistent with experiments was found. The absolute rates typically underestimate measured rates by 50 percent, depending on the experiment considered. For the ratio R(T) = k8(T)/k6(T), the measured T-dependence was found, including a cusp at lower temperatures. The differences between experiments and computations are primarily due to neglect of quantum effects, primarily zero-point effects. For the atomization reaction, leading to 3O(3P), the rates is lower by approximately one order of magnitude compared with experiments, which is a clear improvement over simulations using previous potential energy surfaces computed with smaller basis sets. Non-adiabatic effects are deemed minor for the atom exchange reactions.