Experimental and theoretical studies of the rate coefficients of the reaction O(³P) + HCl at high temperatures

Rate coefficients of the reaction O(³P) + HCl in the temperature range 1093-3197 K were determined using a diaphragmless shock tube. O atoms in the ground electronic ³P states were generated either by photolysis of SO₂ with a KrF excimer laser at 248 nm or by pyrolysis of N₂O with the shock wave. Their concentrations were monitored via atomic resonance absorption excited by emission from a microwave-discharged mixture of O₂ and He. Rate coefficients determined in this work show non-Arrhenius behavior, with values consistent with previously reported measurements for T < 1486 K; they fit well with the equation k₁(T) = (9.27 ± 0.03) × 10^-24 T^3.67±0.18 exp[-(1030 ± 160)/T] cm³ molecule^-1 s^-1; listed errors represent one standard deviation in fitting. Theoretical calculations at the CCSD(T)/6-311+G(d, p) level locate a bent ³A″ (TS1) and a linear ³A′ (TS3) transition state characterized previously. On the basis of the results computed by CCSD(T)/ 6-311+G(3df,2p)//CCSD(T)/6-311+G(d,p), the rate coefficients predicted with conventional transition-state theory, including Eckart-tunneling corrections and with variational transition-state theory including zero- and small-curvature tunneling corrections, all agree satisfactorily with experimental observations.