Kinetics of the Reaction of OH Radicals with Hydrogen Iodide Between 225 and 950 K
Abstract
Reaction OH + HI → I + H2O (1) is an important atmospheric process transforming inactive HI into chemically active iodine atoms. In the present work, the reaction kinetics have been studied in a discharge fast-flow reactor coupled with an electron impact ionization mass spectrometer at nearly 2 Torr total pressure of helium and over a wide temperature range, T = 225–950 K. The reaction rate constant was determined both by a relative rate method (with the OH + Br2 reaction as a reference) and by absolute measurements carried out under pseudo-first order conditions by monitoring the OH consumption kinetics in excess of hydrogen iodide. U-shaped temperature dependence was observed for the reaction rate constant, negative at low temperatures and positive at high temperatures. Recommended expression over the 225–950 K temperature range: k1 = 1.13 × 10−11 exp(354/T) + 6.93 × 10⁻¹¹ exp(−1010/T) cm3 molecule⁻¹ s⁻¹ or in the form of a modified Arrhenius expression, k1 = 4.2 × 10⁻¹² × (T/298)1.36 exp(666/T) cm³ molecule⁻¹ s⁻¹, with a total estimated uncertainty of 15% at all temperatures. The rate constant data obtained in this study are compared with the results of previous experimental works.
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BibTeX
@article{bedjanian2026kinetics,
title = {{Kinetics of the Reaction of OH Radicals with Hydrogen Iodide Between 225 and 950 K}},
author = {Yuri Bedjanian},
journal = {Atmosphere},
year = {2026},
month = oct,
doi = {10.3390/atmos17030301},
url = {https://cnrs.hal.science/hal-05557785v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Kinetics of the Reaction of OH Radicals with Hydrogen Iodide Between 225 and 950 K
AU - Yuri Bedjanian
PY - 2026
DA - 2026/10/07
JO - Atmosphere
DO - 10.3390/atmos17030301
UR - https://cnrs.hal.science/hal-05557785v1
AB - Reaction OH + HI → I + H2O (1) is an important atmospheric process transforming inactive HI into chemically active iodine atoms. In the present work, the reaction kinetics have been studied in a discharge fast-flow reactor coupled with an electron impact ionization mass spectrometer at nearly 2 Torr total pressure of helium and over a wide temperature range, T = 225–950 K. The reaction rate constant was determined both by a relative rate method (with the OH + Br2 reaction as a reference) and by absolute measurements carried out under pseudo-first order conditions by monitoring the OH consumption kinetics in excess of hydrogen iodide. U-shaped temperature dependence was observed for the reaction rate constant, negative at low temperatures and positive at high temperatures. Recommended expression over the 225–950 K temperature range: k1 = 1.13 × 10−11 exp(354/T) + 6.93 × 10⁻¹¹ exp(−1010/T) cm3 molecule⁻¹ s⁻¹ or in the form of a modified Arrhenius expression, k1 = 4.2 × 10⁻¹² × (T/298)1.36 exp(666/T) cm³ molecule⁻¹ s⁻¹, with a total estimated uncertainty of 15% at all temperatures. The rate constant data obtained in this study are compared with the results of previous experimental works.
SN - 2073-4433
SN - 2073-4433
ER -