Measurement of the charged-particle density in combustion-product plasmas by electric probes

The densities of electrons and positive impurity ions have been measured by three independent probe methods in combustion-product plasmas of methane with an alkali additive in air at a temperature of $2200$ K. The positive ion density is observed to be substantially higher than that of the electrons and this is explained by the presence of negative $\rm HCO_3^-$ ions in the plasmas.