Evidence for two independent chemi-ionization processes in the O+C 2H 2 reaction

Abstract

Gases which are known to react rapidly with CH(X 2Π) are added to low pressure mixtures of oxygen atoms and acetylene while monitoring chemi-ion formation. Addition of CH 4 and N 2O, which do not react with oxygen atoms at room temperature, rapidly quench part of the chemi-ion formation, but further additions do not quench it completely. The data can be fit to a simple kinetic model that assumes two independent chemi-ionization reactions. Mass analysis shows that HCO + is the primary ion for both processes. We propose that the non-quenchable chemi-ionization is caused by the reaction of oxygen atoms with the metastable CH(a 4Σ).