Experimental and theoretical study of the recombination reactions of FS(O2)O with FC(O)O and CO

Abstract

The laser flash photolysis technique has been used to study the kinetics of the reactions of FS(O₂)O with FC(O)O and CO at 296 K. Both reactions were found to be essentially in the second-order regime at total pressures ranging from 160 to 1020 mbar of the radical precursors FS(O₂)OF, CO and O₂ and the bath gas SF₆. The FS(O₂)O and FC(O)O radicals were monitored by absorption spectroscopy at 450 and 545 nm. The determined limiting high pressure rate coefficients for the FC(O)O + FS(O₂)O → FC(O)OO(O₂)SF and FS(O₂)O + CO → FS(O₂)OCO reactions are 1.0 ± 0.1 × 10⁻¹² and 4.3 ± 0.9 × 10⁻¹⁷ cm³ molecule⁻¹ s⁻¹. Employing isodesmic reaction schemes with total energies calculated at the B3LYP/6-311++G(3df,p)//B3LYP/6-311++G(d,p) level of theory, enthalpies of formation for FS(O₂)O, FS(O₂)O₂, FS(O₂)OF, FS(O₂)OCO, FS(O₂)OC(O)CO, FS(O₂)OC(O)O₂, FC(O)OO(O₂)SF, FCO, FC(O)O and FC(O)O₂ molecules were derived. An analysis of the rate coefficients in terms of the statistical adiabatic channel model and the transition state theory on potential energy surfaces derived from density functional theory calculations has been carried out.