Theoretical H + O₃ rate coefficients from ring polymer molecular dynamics on an accurate global potential energy surface: assessing experimental uncertainties

Abstract

Thermal rate coefficients and kinetic isotope effects have been calculated for the reaction H + O3 → OH + O2 based on an accurate potential energy surface, using ring polymer molecular dynamics, quasi-classical trajectory and variational transition-state theory.

Insights into the Formation of Hydroxyl Radicals with Nonthermal Vibrational Excitation in the Meinel Airglow

“…Indeed, this PES has been shown to reproduce accurately the reaction kinetics of the H + O 3 reaction. 22 Dynamical calculations that for the first time yield the highly inverted OH vibrational distribution peaked at the highest accessible vibrational state are in much better agreement with experiment 7,10,11 than the previous theoretical study. 17 Moreover, we identified the underlying dynamical mechanism for the extreme OH vibrational excitation using a simple transition-state based model, 23,24 which provides a rational interpretation of the nonstatistical origin of the energy disposal in this reaction.…”

“…In this Letter, we report a detailed QCT dynamic study of the H/D + O 3 reactions on a highly accurate PES recently constructed from a large number of multireference configuration interaction (MRCI) points using the high-fidelity permutation invariant polynomial-neural network (PIP-NN) method. , The MRCI treatment of the PES is essential due to the multireference nature of this system. Indeed, this PES has been shown to reproduce accurately the reaction kinetics of the H + O 3 reaction . Dynamical calculations that for the first time yield the highly inverted OH vibrational distribution peaked at the highest accessible vibrational state are in much better agreement with experiment ,, than the previous theoretical study .…”

“…In the entrance channel, there is a transition state (TS), lying 0.86 kcal/mol above the reactant asymptote, 20 which was shown to control the kinetics, particularly on the temperature dependence of the rate coefficient. 22 As discussed below, it also plays a key role in determining the energy disposal in the reaction. In addition, there is also a very shallow van der Waals well before the system reaches the TS.…”

“…The cis - and trans -HOOO wells are separated with a small barrier, and these features are not expected to impact the dynamics in a significant way, thanks to their low energies relative to the reactant asymptote. In the entrance channel, there is a transition state (TS), lying 0.86 kcal/mol above the reactant asymptote, which was shown to control the kinetics, particularly on the temperature dependence of the rate coefficient . As discussed below, it also plays a key role in determining the energy disposal in the reaction.…”

“…In the same table, the vibration specific rate coefficients are also listed, which can be used in the modeling of energy transfer from OH­( v ) with other atoms and molecules. These state resolved rate coefficients are obtained by the following expression: , where the total rate coefficient is from our recent calculations using the ring-polymer molecular dynamics (RPMD) method, − and are from the fractions in Table .…”