Reactions of the chlorodifluoromethyl radical formed in the photolysis of halogenocarbon + ozone mixtures

Abstract

A photolytic flow system has been used to study the reactions of CF₂Cl with ozone. The radical was generated by ultraviolet photolysis of O₃+ CF₂Cl₂ mixtures. Concentrations of reactants and products were determined by quadrupole mass spectrometry, and varying contact times obtained by varying the distance between the photolysis lamp and the sampling orifice. Quantum yields for ozone loss and for ClO production were then analysed to provide kinetic information. Comparison of the experimental data with computer models of the reaction system show that a plausible reaction sequence is [graphic omitted] with k₁₂(298 K)=(1.4 ± 0.7)× 10^–14 cm³ molecule^–1 s^–1, and both k_10a and k₁₁ not lower than 1 × 10^–13 cm³ molecule^–1 s^–1. Thus, the chlorine atom in CF₂Cl can be converted into ClO, which has implications for the ClO_x catalytic O₃ destruction cycle in stratospheric chemistry. CF₂O is produced in reactions of CF₂Cl and not in the reaction of O(¹D) with CF₂Cl₂.