Hydrogen atom + oxygen + M (= N2, H2O, Ar) three-body rate coefficients at 298-750 K

Abstract

Three-body rate coefficients for reactions of H + 0 2 + M where M = Nz and HzO have been measured in a high-temperature flow reactor as a function of temperature up to 750 K. Room-temperature rate coefficients for M = Ar have also been quantified. The rate coefficients are measured by the flash photolysis method where atomic hydrogen is produced by excimer laser photolysis of precursor molecules (HzS or HzO) and then probed by either laser-induced fluorescence or resonance absorption. The rate coefficient measurements for nitrogen (298-580 K) can be described by the Arrhenius expression exp[(825 f 130)/T] cm6 molecuk2 s-l. Rate coefficients measured for water are k~~o ( S 7 5 ) = (1.2 f 0.3) X k~,o(650) = (1.0 f 0.3) X 10-31, and k~~o ( 7 5 0 ) = (1.22;) X cm6 molecule-2 s-'. Room-temperature measurements for Ar gave a rate coefficient of kk(298) = (2.1 f 0.2) X 10-32.= (2.9 f 0.8) X

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume I - gas phase reactions of O<sub>x</sub>, HO<sub>x</sub>, NO<sub>x</sub> and SO<sub>x</sub> species

“…The preferred values are an average of the results from Kurylo (1972), Wong and Davis (1974), , Hsu et al (1989) and Carleton et al (1993). There is a single study of the full falloff curve which leads to k ∞ = 7.5×10 −11 cm 3 molecule −1 s −1 at 298 K and a broadening factor of F c = 0.55 ± 0.15 at 298 K. Theoretical modeling (Harding et al, 2000; using an ab initio potential energy surface gives k ∞ = 9.5×10 −11 (T /300) 0.44 cm 3 molecule −1 s −1 and F c = 0.5 over the range 200-2000 K. Reliability log k = ±0.1 at 298 K. (E/R) = ±100 K.…”

The Temperature and Pressure Dependence of the Reactions H + O2 (+M) → HO2 (+M) and H + OH (+M) → H2O (+M)

“…The results from these calculations are included in Figure 1. Ascanbeseen,theCAS+1+2modelpredictedaBorn-Oppenheimer barrier to reaction of about 0.1 kcal mol -1 relative to the energy 82 Bates et al, 7 Baulch et al, 9 Carleton et al, 83 Cobos et al, 6 Davidson et al, 84 Hanning-Lee et al, 85 Hsu et al, 86 Michael et al, 18 and Mueller et al 87 of the reactants, which obviously is not correct. The situation improved when the Davidson correction was included, but still, the calculation predicted a small barrier to reaction below the energy of the reactants.…”

“…The plotted low-pressure and highpressure limiting rate coefficients are the values preferred by the IUPAC panel. 9 References: Baulch et al, 9 Carleton et al, 83 Cobos et al, 6 Hahn et al, 8 Hsu et al, 86 Kurylo, 88 Michael et al, 18 and Wong and Davis. 89 as bath gases, respectively.…”

Kinetics and modeling of the H2O2NOx system

“…With the exception of the value for h 5 ,~2 , all those rate constants were taken from the literature without adjustment. The value of h 5 , N Z which was used to generate the predictions was [8,11,14,15,201 is not important because the low concentration of this species (mole fraction <0.008) makes the calculations insensitive to this value. Figure 5 shows and, as shown in Figure 5, there are regions where the predictions are substantially independent of k35.…”