Dissociative excitation of CF4, CCl4, and chlorofluoromethanes by collisions with argon and helium active species

Abstract

Dissociative excitation of CFnCl4–n (n=0–4) by collisions with Ar and He active species has been studied by observing uv and visible emissions in the Ar and He afterglows. Emissions from such excited fragments as Cl*, Cl*2, CF*, CCl*, CCl+*, ArCl*, CF*2, CCl*2, CFCl*, and CF*3 were observed. New continuous bands which may be related to Cl*2, CFCl*, CCl*n(n=2,3), and CCl+*n(n=2,3) were found in the reactions of CFCl3 and CCl4. The effects of ion trapping and SF6 addition into the discharge flow indicated that the excited species were produced from primary reactions by the metastable Ar(3P2) and He(2 3S) atoms and (Ar+)* and He+ ions and/or secondary reactions via electron–ion recombination processes. The emission rate constants have been determined for the primary reactions of Ar(3P2), He(2 3S), and He+ with CFnCl4–n (n=0–3). A comparison between the observed emission rate constants and known total quenching rate constants indicated that dissociative excitation processes are minor exit channels (≤4.6%).