Experimental and Theoretical Studies of the Rate Coefficients of the Reaction O(3P) + HCl at High Temperatures

Rate coefficients of the reaction O( 3 P) + HCl in the temperature range 1093−3197 K were determined using a diaphragmless shock tube. O atoms in the ground electronic 3 P states were generated either by photolysis of SO 2 with a KrF excimer laser at 248 nm or by pyrolysis of N 2 O with the shock wave. Their concentrations were monitored via atomic resonance absorption excited by emission from a microwave-discharged mixture of O 2 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 k 1 ( T ) = (9.27 ± 0.03) × 10 -24 T 3.67±0.18 exp[−(1030 ± 160)/ T ] cm 3 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 3 A‘ ‘ (TS1) and a linear 3 A‘ (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.