New insights into methane-oxygen ion chemistry

Detailed relative cation mole fraction measurements were performed in premixed 30 torr flat flames of methane. Relative ion mole fraction profiles showed strong dependence of the identity of dominant ions and their spatial distribution on the flame equivalence ratio. The prediction of notably faster H3O + decay was due to inadequacies in the ion chemistry model. CH3O2 + and C2H7O+ were among the major ions in lean flame and need to be included in future ion chemistry models. For the first time ions at m/z = 53 ( + 71) reflecting contributions from C3HO+ and C4H5+ were observed in stoichiometric and rich flames.