The gas phase reactions of the NO3 radical, a ubiquitous constituent of nighttime atmospheres with the reduced sulfur compounds COS, CS2, CH3SH, C2H5SH, and CH3SSCH3 have been investigated. Using a relative rate technique and long path length Fourier transform infrared (FT‐IR) absorption spectroscopy, rate constants for these reactions have been determined at 297 ± 2 K in one atmosphere of air. The resulting rate constants (in units of 10−13 cm3 molecule−1 s−1) are: COS, <0.0004; CS2, <0.008; CH3SH, 10 ± 3; C2H5SH, 12 ± 3; and CH3SSCH3, 0.42 ± 0.09. A number of products from these reactions were determined using FT‐IR absorption spectroscopy and combined gas chromatography/mass spectrometry. Atmospheric implications of these kinetic and product data are discussed.
The gas phase reaction of OH radicals with hydrogen iodide (HI) has been studied using a Laser Photolysis-Resonance Fluorescence (LP-RF) apparatus, recently developed in our group.The measured rate constant at 298 K was (2.7 2 0.2) X lo-" cm3 molecule-' s-'. This rate constant is compared with the ones of the reactions OH + HC1 and OH + HBr. The role of the reaction OH + HI in marine tropospheric chemistry is discussed.In addition, the LP-RF apparatus was tested and validated by measuring the following rate constants (in cm3 molecule-' s-' units): k(OH + HN03) = (1.31 2 0.06) x at P = 27 and 50 Torr of argon and k(OH + C3H8) = (1.22 ? 0.08) x lo-''. These rate constants are in very good agreement with the literature data.
The kinetics of the reaction of chlorine nitrate (ClONO2) with water vapor have been investigated in large‐volume (2500‐L and 5800‐L) Teflon or Teflon‐coated environmental chambers to assess the importance of this reaction as a loss process for odd nitrogen in the stratosphere. These data show that the upper limit rate constant for the homogeneous gas phase reaction between ClONO2 and H2O is <2 × 10−21 cm³ molecule−1 s−1 at 298 ± 1 K. With this rate constant, the homogeneous reaction of ClONO2 with water vapor will be of negligible importance under stratospheric conditions.
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