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Author(s):   Isshiki, N.; Murakami, Y.; Tsuchiya, K.; Tezaki, A.; Matsui, H.
Title:   High-Temperature Reactions of O + COS and S + SO2 Abstraction Versus Substitution Channels
Journal:   J. Phys. Chem. A
Volume:   107
Page(s):   2464 - 2469
Year:   2003
Reference type:   Journal article
Squib:   2003ISS/MUR2464-2469

Reaction:   SO2 + SSO + SO
Reaction order:   2
Temperature:   1250 - 1600 K
Pressure:  2.50E13 - 9.50E13 bar
Rate expression:   9.77x10-12 [cm3/molecule s] e-37800 [±8200 J/mole]/RT
Uncertainty:   2.0999999
Category:  Experiment
Data type:   Absolute value measured directly
Pressure dependence:   Rate constant is pressure independent
Experimental procedure:   Shock tube
Excitation technique:   Thermal
Time resolution:   In real time
Analytical technique:   Vis-UV absorption
Comments:   Combined experimental (shock tube) and ab initio study. Used energies from G2M calculations with B3LYP/cc-pVTZ geometries in ab initio part of work for COS+O reaction (only). Absolute rate constants for the COS + O reaction pathways from ab initio calculations are in poor agreement (2x low at high temp, 4x low at low temp) with calculated barrier of about 37 kJ/mol while expt value is about 23 kJ/mol. However, branching ratio of COS +O -> COS + SO versus CO2 + S agrees well (25%) with experimental determination, which is on the order of 0.22-0.27 (for CO2 + S products). Rate expressions based on ab initio calculations are not reported in paper, but a figure shows a comparison with the experimental data.

S and O atoms formed by 248 nm KrF excimer laser photolysis of SO2. O and S atoms detected by atomic resonance absorption. Temperature range 1250-1600 K. Total pressure 2.5-9.5E18 molecules/cm3 Argon. Typical 50 ppm COS, 1000 ppm SO2.

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Rate constant values calculated from the Arrhenius expression:

T (K)k(T) [cm3/molecule s]
1250 2.57E-13
1275 2.76E-13
1300 2.96E-13
1325 3.16E-13
1350 3.37E-13
1375 3.58E-13
1400 3.80E-13
1425 4.02E-13
1450 4.25E-13
1475 4.48E-13
1500 4.72E-13
1525 4.96E-13
1550 5.20E-13
1575 5.45E-13
1600 5.70E-13