Rate Coefficient Measurements for the CH3SCH2OO Radical + NO Reaction Between 313 and 413 K

The CH₃SCH₂OO radical is a key intermediate formed in the gas-phase oxidation of dimethyl sulfide (CH₃SCH₃, DMS). In this study, the rate coefficient, k₁(T), for the gas-phase CH₃SCH₂OO + NO reaction was measured using a pulsed laser photolysis–iodide chemical ionization mass spectrometry (CIMS) detection competitive reaction method over the temperature range 313–413 K. Hydroperoxymethyl thioformate (HOOCH₂SCHO, HPMTF) formed following a H-shift reaction of the CH₃SCH₂OO radical was monitored using CIMS as a function of added NO concentration. The k₁(T) results are described by the Arrhenius expression k₁(313–413 K) = (1.43 ± 0.29) × 10⁻¹² exp((510 ± 160)/T) cm³ molecule⁻¹ s⁻¹, where the quoted uncertainties are 2σ and the pre-exponential coefficient uncertainty includes estimated systematic errors. An extrapolation to room temperature yields k₁(298 K) = 7.9 × 10⁻¹² cm³ molecule⁻¹ s⁻¹. Results from this study are compared with previous room temperature and temperature dependent (261–400 K) studies. The reaction rate coefficient obtained in this work is recommended for use in atmospheric chemistry and climate models.