Kinetic and theoretical investigations of the S + NO2 reaction

✍ Scribed by Kristopher M. Thompson; Yide Gao; Paul Marshall

• Publisher: John Wiley and Sons
• Year: 2011
• Tongue: English
• Weight: 419 KB
• Volume: 44
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20612

✦ Synopsis

Ground state atomic sulfur was generated by 193-nm laser photolysis of CS 2 precursor in Ar bath gas, in the presence of a large excess of NO 2 under pseudo-first-order conditions. Decays of S( 3 P J ) were monitored over 292-656 K and pressures of 14-535 mbar. No pressure dependence was observed, and the second-order constants are summarized as k(T ) = 1.9 × 10 -11 exp(+4.1 kJ mol -1 )/RT cm 3 molecule -1 s -1 , with a 95% confidence interval of ±7%. The potential energy surfaces for SNO 2 and S(NO 2 ) 2 were explored using QCISD/6-311G(d,p) theory for geometries and frequencies, followed by single-point calculations based on coupled-cluster theory and extrapolation of results with cc-pV(T+d)Z and cc-pV(Q+d)Z basis sets to the complete basis set limit. Corrections were made for scalar relativistic effects and core-valence correlation. A mechanism involving initial barrierless addition of S to the N atom in NO 2 , followed by fast dissociation to SO + NO, is consistent with the observed lack of pressure dependence and a Rice-Ramsperger-Kassel-Marcus estimate of the dissociation rate of SNO 2 compared to collisional stabilization.