Abstract
Rate coefficients for the reaction of OH with Cl-2, (k(1)), Br-2, (k(2)) and I-2, (k(3)), were measured under pseudo-first-order conditions in OH. OH was produced by pulsed laser photolysis of H2O2 (or HNO3) and its temporal profile was monitored by laser-induced fluorescence. The measured rate coefficients for k(1) (231-354 K) and k(2) (235-357 K) are:k(1) (T) = (3.77 +/- 1.02) X 10(-12) exp-(1228 +/- 140)/T cm(3) molecule(-1) s(-1)k(2) (T) = (1.98 +/- 0.51) X 10(-11) exp(238 +/- 70)/T cm(3) molecule(-1) s(-1)k(3) was independent of temperature between 240 and 348 K with an average Value of (2.10 +/- 0.60) X 10(-10) cm(3) molecule(-1) s(-1). The quoted uncertainties are 2 sigma (95% confidence limits, 1 sigma(A) = A sigma(lnA)) and include estimated systematic errors. Our measurements significantly improve the accuracy of k(1). This is the first report of a slight negative temperature dependence for k(2) and of the temperature independence of k(3). (C) 1999 John Wiley & Sons, Inc.*
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