The kinetics of the disproportionation reactions of OH and OD radicals, OH + OH → O + H2O (1), OD +
OD → O + D2O (3), have been studied by the mass spectrometric discharge-flow method at temperatures
between 233 and 360 K and at total pressure of 1 Torr of helium. The following Arrhenius expressions were
obtained: k
1 = (7.1 ± 1.0) × 10-13exp[(210 ± 40)/T] and k
3 = (2.5 ± 0.5) × 10-13exp[(170 ± 60)/T] cm3
molecule-1 s-1. Reaction 4 between OH and OD radicals was also investigated and the same rate constant as
for reaction 1 was measured. Both the observed temperature dependence of k
1 and the measured kinetic
isotopic effect (k
1/k
3) are compatible with the mechanism proposed in a previous theoretical study (Harding,
L. B.; Wagner, A. F. 22nd International Symposium on Combustion, 1988). In addition, a temperature-independent rate coefficient of (1.20 ± 0.25) × 10-10 cm3 molecule-1 s-1 was measured for the reaction D
+ NO2 → OD + NO in the temperature range 230−365 K.
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