HTP kinetics studies of the reactions of O(2 3P J) atoms with H2 and D2 over wide temperature ranges

The O+H2(1) and O+D2(2) reactions have been investigated, using the high-temperature photochemistry (HTP) technique, over the 350 to 1420 and 390 to 1420 K temperature ranges, respectively. O(2 3PJ) atoms were generated from flash photolysis of CO2 and monitored by time-resolved atomic resonance fluorescence with pulse counting. Above 430 K the rate coefficients are given by k1(T)=7.3×10−21 (T/K)2.93 exp(−2980 K/T) cm3 molecule−1 s−1 and k2(T)=3.1×10−16 (T/K)1.65 exp (−5260 K/T) cm3 molecule−1 s−1. Combination of our data with those from other experiments which isolated the reactions from secondary processes yields our recommendations k1(T)=1.5×10−12 exp (−3540 K/T)+3.7×10−10 exp (−7450 K/T) cm3 molecule−1 s−1 (300 K≤T≤2500 K) and k2(T)=1.4×10−12 exp(−4260 K/T) +2.9×10−10 exp (−7780 K/T) cm3 molecule−1 s−1 (390 K≤T≤1420 K). Accuracy assessments are discussed in the text. k1(T), k2(T), and the kinetic isotope effect compare well with calculations based on recent ICVT/LAG and CEQB ab initio methods, which suggest that the first terms of the double exponential expressions approximate the tunneling contributions.