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Kinetics and mechanism of HO/sub 2/ and DO/sub 2/ disproportionations

Journal Article · · J. Phys. Chem.; (United States)
DOI:https://doi.org/10.1021/j150654a029· OSTI ID:6695924
The HO/sub 2/ + HO/sub 2/ and DO/sub 2/ + DO/sub 2/ reactions in the gas phase have been studied by the flash photolysis/UV absorption technique. Rate constants were measured at pressures between 100 and 700 torr of Ar and N/sub 2/ at temperatures between 230 and 420 K, and with up to 10 torr of added water vapor. The overall disproportionation rate constant can be expressed as the sum of pressure-independent and pressure-dependent terms. The experimental uncertainty in k/sub 1/ and k/sub 2/, including systematic errors, is 25% (one standard deviation). The enhancement of the HO/sub 2/ + HO/sub 2/ rate constant in the presence of added water vapor was studied over the temperature range 250-298 K and found to contribute a multiplicative term (1 + 1.4 x 10/sup -21/ exp(2200/T)(H/sub 2/O)) to the rate constant expressions. The mechanism of the HO/sub 2/ + HO/sub 2/ reaction was investigated with a two-channel RRKM model which suggested that the binding energy of the HO/sub 4/H intermediate lies in the range of 12-20 kcal mol/sup -1/ relative to HO/sub 2/ reactants. 35 references, 8 figures, 7 tables.
Research Organization:
California Inst. of Tech., Pasadena
OSTI ID:
6695924
Journal Information:
J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 88:10; ISSN JPCHA
Country of Publication:
United States
Language:
English