Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide The cross reaction between the free radicals OH and HO 2 plays a critical role in a wide range of environments, including combustion and the atmospheres of Earth and Mars. In the middle atmosphere on Earth, it is the ultimate terminating step of odd-hydrogen chemistry, which has significant implications for the abundance of ozone. Recent laboratory measurements have brought established rate coefficients into question, introducing additional uncertainties into chemical models of the upper stratosphere and mesosphere. In this work, we present measurements of the rate coefficient from 265 – 350 K using high-resolution infrared and ultraviolet kinetic spectroscopy. A scheme was developed which almost entirely avoids interfering reactions, providing a direct measurement of the decay of OH due to HO 2 and reduces uncertainties associated with absolute calibration of OH and HO 2 concentrations. We find a room temperature rate coefficient of k (295) = (9.0 ± 1.9) × 10 –11 cm 3 molecule –1 s –1 (1σ error) and a slight temperature dependence over 265–330 K with an E /R of −155 ± 50 K.
Institutions: California Institute of Technology, Jet Propulsion Laboratory
Language: English
Subfield: Atmospheric Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W4409655243