Rate constants for the reaction O+D2→OD+D by the flash photolysis–shock tube technique over the temperature range 825–2487 K: The H2 to D2 isotope effect

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Abstract
Rate constants for the reaction of O(3P) atoms with deuterium, O+D2→OD+D, have been measured over the temperature range 825–2487 K. The experimental method that has been used is the flash photolysis–shock tube (FPST) technique. This technique utilizes atomic resonance absorption spectroscopy (ARAS) to monitor O‐atom depletion in the presence of a large excess of reactant, D2. The measurement is made in the stagnant reflected shock wave region. Thus, shock heating simply serves to prepare the gas density and temperature for a flash photolytically induced absorption photometric experiment. The results that have been obtained between 825 and 2487 K can be represented by the Arrhenius expression: k=(3.22±0.25)×10−10 exp(−7293±98 K/T) cm3 molecule−1 s−1. The average deviation of the present data from this equation is ±17%. An alternative three parameter expression that represents the data to within ±16% is k=1.95×10−15 T1.45 exp(−5250 K/T) cm3 molecule−1 s−1. When the recent results of Zhu, Arepalli, and Gordon (the preceding paper) are considered, a three parameter expression can be determined for the temperature range, 343–2487 K. This combined result is k=2.43×10−16 T1.70 exp (−4911 K/T) cm3 molecule−1 s−1. The average deviation of the data from this equation is ±16%, whereas the data of Gordon and co‐workers agree to within ±5%. The combined result is compared to earlier experimental results and, also, to theoretical calculations by Bowman, Wagner, Walch, and Dunning; Garrett and Truhlar; and Joseph, Truhlar, and Garrett. The present result is used along with recent data for O+H2 to specify the experimental isotope effect, kH2/kD2, over the experimental temperature range. Lastly, the experimental rate constant ratio is compared to the theoretical predictions.

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