An extensive study of O(1D) reaction rate coefficients for key ozone depleting substances and greenhouse gases

A key stratospheric loss process for ozone depleting substances (ODSs) and greenhouse gases (GHGs) is their gas-phase reaction with electronically excited oxygen atoms, O(¹D). Although numerous O(¹D) reactions have been studied in the past, large uncertainties in the recommended rate coefficients and reactive yields, i.e., loss of ODS or GHG, for use in atmospheric modeling still exist for a number of key compounds. Our understanding of the coupling of atmospheric chemistry and climate-change requires the most accurate reaction rate coefficient data to be used in climate-change model calculations. In this presentation, results from an extensive laboratory study of the total reaction rate coefficient, corresponding to loss of O(¹D), and reactive rate coefficients, corresponding to the loss of the reactant compound, will be presented for the ODSs: CFCl₃ (CFC-11), CF₂Cl₂ (CFC-12), CFCl₂CF₂Cl (CFC-113), CF₂ClCF₂Cl (CFC-114), CF₃CF₂Cl (CFC-115), HClCF₂ (HCFC-22), CH₃CClF₂ (HCFC-142b); GHGs: CHF₃ (HFC-23), CHF₂CF₃ (HFC-125), CF₃CHCF₃ (HFC-227ea), and CF₃CH₃ (HFC-143a); and the persistent (long-lived) GHGs: NF₃, SF₅CF₃, C₂F₆, c-C₄F₈, n-C₅F₁₂, and n-C₆F₁₄. The results from this work will be compared with results from previous studies and discrepancies discussed along with the atmospheric implications of the improved kinetic dataset on the atmospheric lifetimes of these compounds.