Product distributions in the reactions of excited noble-gas atoms with halogen-containing compounds

The products of the reactions of electronically excited Ar( ³P₀, ³P₂), Kr(³P ₂), and Xe(³P₂) atoms with the chloromethanes, chlorofluoromethanes, CF₃H, CF₂HCl, CFHCl₂, CF₂Cl-CF₂Cl, CF₃-CCl₃, and HCl have been investigated by the discharge-flow technique, using atomic resonance fluorescence to probe dissociation channels and emission spectroscopy. Energy transfer leading to cleavage of C-H or C-Cl bonds is extremely efficient, particularly in the reactions of Xe(³P₂) with CF ₂Cl₂ and CFCl₃ and of Ar(³P _0,2) with CFCl₃, in which more than two Cl atoms are released per primary reactive event. The observation of contrasting behavior in the reactions of Xe(³P₂) with CF₃H and CF ₄ has led to the discovery of a qualitative correlation between the rate constants, the products of the energy transfer process, and the accessibility of dissociative or ionizing states of the reagent molecule, as revealed by its vacuum UV absorption spectrum.