Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 1 1 2001 10.5194/acpd-1-23-2001 http://www.atmos-chem-phys-discuss.net/1/23/2001/ http://www.atmos-chem-phys-discuss.net/1/23/2001/acpd-1-23-2001.html http://www.atmos-chem-phys-discuss.net/1/23/2001/acpd-1-23-2001.pdf 23 41 2001-09-03 298 K rate coefficients for the reaction of OH with i-C₃H₇I, n-C₃H₇I and C₃H₈ S. A. Carl J. N. Crowley Max-Planck-Institut f ¨ ur Chemie, Division of Atmospheric Chemistry, Postfach 3060, D-55020 Mainz, Germany Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium The kinetics of the title reactions were investigated using the laser photolysis - resonance fluorescence method, employing the sequential two-photon dissociation of NO₂ in the presence of H₂ as the OH source. The 298 K rate constant for OH + C₃H₈ was found to be (1.15±0.1) × 10^-12 cm³ s^-1, in excellent agreement with the literature recommendation, and with a separate determination using HNO₃ photolysis at 248 nm as the OH source. The 298 K rate constants for OH + n-C₃H₇I and i-C₃H₇I were measured for the first time and found to be (1.47±0.08) and (1.22±0.06) × 10^-12 cm³ s^-1, respectively. The errors include an assessment of systematic error due to concentration measurement, which, for the propyl-iodides was minimised by on-line UV-absorption spectroscopy. The implications of these results for the reactive iodine budget of the marine boundary layer are discussed.