Rate constant for the reaction of O(3P) with H2 by the flash photolysis—shock tube and flash photolysis—resonance fluorescence techniques; 504K≤T≤2495K

The rate constant for the reaction, O ( P 3 ) + H 2 → O H + H , ( 1 ) was measured over the temperature range of 504K to 2495 K by two independent experimental methods. The flash photolysis-shock tube (FP-ST) technique, combined with atomic resonance absorption spectroscopy (ARAS), was used over the temperature range 880K to 2495K. The results from the FP-ST work, expressed in simple Arrhenius form, are: k 1 ( T ) = ( 3.1 ± 0.2 ) × 10 − 10 exp ⁡ ( − 13620 ± 170 / R T ) c m 3 molecule − 1 s − 1 , where the units of R in this and succeeding expressions are cal mole −1 K −1 . The flash photolysis-resonance fluorescence (FP-RF) technique was utilized to measure rate constants from 504K to 923K. Results from the FP-RF experiments, also expressed in simple Arrhenius form, are: k 1 ( T ) = ( 7.2 ± 0.4 ) × 10 − 11 exp ⁡ ( − 10430 ± 70 / R T ) c m 3 molecule − 1 s − 1 . These kinetic results for the reaction of O( 3 P) with H 2 exhibit non-Arrhenius behavior. This conclusion is confirmed by the recent kinetic data of Presser and Gordon (297K≤T≤471K). The combined results from these three data sets are expressed by the three parameter fit: k 1 ( T ) = 8.4 × 10 − 20 T 2.67 exp ⁡ ( − 6290 / R T ) c m 3 molecule − 1 s − 1 . The estimated error in this expression is about ±30% over the entire temperature range, 297K to 2495K. Rate constants for reaction (1) from recent ab initio calculations are in excellent agreement with these experimental results.