The effects of applying electric fields on the mass spectrometric sampling of positive and negative ions from a flame at atmospheric pressure

Flames are plasmas, because they contain free electrons and both positive and negative ions. The concentrations of ions in a flat flame, burning at 1bar, have been measured by continuously sampling the hot (2400K) gas into a mass spectrometer at low pressure. The voltage, Δϕ, between the metallic burner and the plate holding the metallic sampling nozzle was varied; also, the flame was seeded with an alkali metal and doped with much larger quantities (mole fraction ⩽1.7%) of chlorine. Currents of ions such as K+ and Cl− were measured with the mass spectrometer for different Δϕ and indicated that the sampling nozzle repels free electrons, when it is at a negative potential with respect to the burner (Δϕ