Quantum dynamics of the O + OH -> H + O2 reaction at low temperatures

TL;DR

This study uses quantum dynamics calculations to analyze the O + OH reaction at low temperatures, revealing stable rate coefficients below 40 K and population of excited O2 vibrational states, with implications for interstellar oxygen chemistry.

Contribution

First quantum dynamics calculations on two PES representations for the reaction, showing temperature-independent rate coefficients below 40 K and vibrational excitation of O2.

Findings

Rate coefficients are stable from 10-39 K.

Excited vibrational levels of O2 are populated.

Rate coefficients are sensitive to energy resolution at low temperatures.

Abstract

We report quantum dynamics calculations of the O + OH -> H + O2 reaction on two different representations of the electronic ground state potential energy surface (PES) using a time-independent quantum formalism based on hyperspherical coordinates. Calculations show that several excited vibrational levels of the product O2 molecule are populated in the reaction. Rate coefficients evaluated using both PESs were found to be very sensitive to the energy resolution of the reaction probability, especially at temperatures lower than 100 K. It is found that the rate coefficient remains largely constant in the temperature range 10-39 K, in agreement with the conclusions of a recent experimental study [Carty et al., J. Phys. Chem. A 110, 3101 (2006)]. This is in contrast with the time-independent quantum calculations of Xu et al. [J. Chem. Phys. 127, 024304 (2007)] which, using the same PES, predicted two orders of magnitude drop in the rate coefficient value from 39 K to 10 K. Implications of our findings to oxygen chemistry in the interstellar medium are discussed.