Kinetic studies of excited singlet oxygen atom O( 1 D) reactions with ethanol

The multichannel reaction of excited singlet oxygen atom with ethanol, O( 1 D) + C 2 H 5 OH (1), was studied in a photolysis flow reactor coupled with mid‐infrared Faraday rotation spectroscopy (FRS) and UV‐IR direct absorption spectroscopy (DAS) at 297 K with reactor pressures of 60, 120, and 150 Torr (bath He). The excited singlet oxygen atom was generated through the photolysis of O 3 at 266 nm. The photon flux and O( 1 D) concentrations were determined by in situ actinometry based on O 3 depletion. Temporal profiles of OH and H 2 O were monitored via DAS signals at ca. 3568.62 and 3568.29 cm −1 , while temporal profiles of HO 2 were measured via FRS signals at ca. 1396.90 cm −1 . The branching ratios of the target reaction (1) were determined by fitting temporal profiles to simulations from an in‐house reaction mechanism. Two major reaction channels were identified as CH 3 CHOH + OH and CH 3 O + CH 2 OH, and their branching ratios were determined as 0.46 ± 0.12 and 0.42 ± 0.11, respectively. A specific HO 2 + RO 2 reaction between HO 2 and O 2 CH 2 CH 2 OH (β‐RO 2 ) at the low‐temperature range is estimated in this work as HO 2 + O 2 CH 2 CH 2 OH ⟶ products with a rate constant of 7 × 10 −12 cm 3 molecule −1 s −1 .