Kinetics of the reactions of atomic chlorine with H2S, HS and OCS

Abstract

The Cl + H₂S system has been examined in a discharge–flow system with detection of free-radical and molecular species via molecular-beam-sampling mass spectrometry. The time-dependence of the product species HS, SCl and S₂, detected in the presence of an excess of Cl, has been determined. The rate constant for the reaction Cl + H₂S [graphic omitted] HS + HCl (1), k₁=(5.1 ± 0.7)× 10^–11 cm³ molecule^–1 s^–1(1 σ) at 296 K was determined from the decay of the H₂S peak in an excess of Cl. By monitoring the HS peak, the ratio k₂/k₁ was measured, where k₂ refers to the reaction Cl + HS [graphic omitted] S + HCl. (2). The measured value of k₂/k₁= 2.2 ± 0.4 and the above value of k₁ leads to k₂=(1.1 ± 0.3)× 10^–10 cm³ molecule^–1 s^–1(1 σ). An upper limit on the rate constant at 298 K of the reaction Cl + OCS [graphic omitted] CO + SCl (3), k₃ < 4 × 10^–15 cm³ molecule^–1 s^–1 was also obtained.

The results for k₁ are compared with previous measurements employing infrared chemiluminescence to monitor HCl or resonance fluorescence to monitor atomic chlorine.