Reactions of O(21D2) and O(23PJ) with halogenomethanes

Abstract

Product branching ratios for the reaction of O(2¹D₂) with the halogenomethanes CF₃Cl, CF₃Br, CF₃I and CF₂HCl are presented. The dominant channel is shown to be abstraction yielding a halogen oxide. This contrasts with the behaviour observed with hydrocarbons, where insertion into C–H bonds dominates. Quenching of O(2¹D₂) to the ground state is also observed with the halogenomethanes and accounts for ≈ 30% of the total removal cross-section.

Reaction of O(2¹D₂) with CF₂HCl leads to the formation of CIO (55%) and to the elimination of HCl (40%). The latter process is accompanied by the formation of CF₂ and O(2³P_J).

The reactions of O(2¹D₂) are compared with those for O(2³P_J), where these are known, and the absolute rate for reaction of O(2³P_J) with CF₃I is determined as (1.1 ± 0.3)× 10^–11 cm³ molecule^–1 s^–1 at 300 K.

The results are discussed in terms of the main topological features on the potential surfaces involved.