Temperature dependence of the rate constant and branching ratio for the OH+ClO reaction

Abstract

The overall rate constant and branching ratio for the OH + ClO reaction have been measured using the turbulent flow technique with high-pressure chemical ionization mass spectrometry for the detection of reactants and products. At 298 K and ca. 100 Torr pressure, the overall rate constant was determined to be (1.46 ± 0.23) × 10 ⁻¹¹ cm ³ molecule ⁻¹ s ⁻¹ . The temperature dependence of the rate constant was investigated between 205 and 298 K, yielding the following Arrhenius expression: (5.5 ± 1.6)×10 ⁻¹² exp[(292 ± 72)/T] cm ³ molecule ⁻¹ s ⁻¹ . For the branching ratio studies OD was used instead of OH, making it possible to observe directly the production of DCl from the minor channel of the OD + ClO reaction. The temperature dependence of the rate constant for this minor channel was investigated between 210 and 298 K, yielding the following Arrhenius expression: (1.7 ± 0.3) × 10 ⁻¹³ exp[(363 ± 50)/T] cm ³ molecule ⁻¹ s ⁻¹ . The branching ratio for the DCl channel was found to range from 0.05 ± 0.02 at 298 K to 0.06 ± 0.02 at 210 K.