Pressure dependence of the absolute rate constant for the reaction OH+C2H2 from 228 to 413 K

The pressure dependence of absolute rate constants for the reaction of OH +C2H2→ products has been examined at five temperatures ranging from 228 to 413 K. The experimental technique which was used is flash photolysis–resonance fluorescence (FP–RF). OH was produced by water photolysis and hydroxyl resonance fluorescent photons were measured by multiscaling techniques. The results indicate that the low pressure bimolecular rate constant is ∼4×10−13 cm3 molecule−1 s−1 over the temperature range studied. A substantial increase in the bimolecular rate constant with an increase in pressure was observed at all temperatures except 228 K. This indicates the importance of initial adduct formation and subsequent stablization. The high pressure results are well represented by the Arrhenius expression (kbi)∞=(6.8.3±1.19)×10−12 exp(−646±47/T) cm3 molecule−1 s−1. The present results are compared to previous investigations and are theoretically discussed. The implications of these results on modeling of terrestrial and planetary atmospheres and also in combustion chemistry are discussed.