The kinetics study of the S + S2 â S3 reaction by the chaperone mechanism.
J Chem Phys
; 134(15): 154508, 2011 Apr 21.
Article
em En
| MEDLINE
| ID: mdl-21513396
ABSTRACT
The recombination of S atoms has been found to be stepwise from the smallest unit, the elemental S atom, to the most abundant molecule S(8). The reaction between S + S(2) â S(3) has not been reported either experimentally or by theory, but may be a key intermediate step in the formation of sulfur aerosols in low-O(2) atmospheres. In this work, the kinetics of this reaction is reported with Ar gas used as the chaperone molecule in the production of S(3) via two complex intermediates SAr + S(2) and S(2)Ar + S. Quasi-classical and classical trajectory methods are used. The rate constant of the S + S(2) + Ar â S(3) + Ar reaction is determined to be 2.66 × 10(-33) cm(6) mol(-1) s(-1) at 298.15 K. The temperature dependence of the reaction is found to be 2.67 × 10(-33) exp[143.56(1∕T-1∕298.15)]. The second-order rate constant of S + S(2) â S(3) is 6.47 × 10(-14) cm(3) molecule(-1) s(-1) at 298.15 K and the Arrhenius-type rate constant is calculated to be 6.25 × 10(-14) exp[450.15(1∕T-1∕298.15)] cm(3) molecule(-1) s(-1). This work provides a rate coefficient for a key intermediate species in studies of sulfur formation in the modern Venus atmosphere and the primitive Earth atmosphere, for which assumed model rate coefficients have spanned nearly 4 orders of magnitude. Although a symmetry-induced mass-independent isotope effect is not expected for a chaperone mechanism, the present work is an important step toward evaluating whether mass-independence is expected for thiozone formation as is observed for ozone formation.
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Base de dados:
MEDLINE
Idioma:
En
Revista:
J Chem Phys
Ano de publicação:
2011
Tipo de documento:
Article
País de afiliação:
Estados Unidos