Mass Spectrometric Sampling of Combustion Plasmas

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Abstract
An arrangement is described whereby atmospheric pressure flame plasmas are sampled into a quadrupole mass spectrometer for analysis and identification of each ion present. The principal difficulty encountered is that of obtaining a fully representative sample of gas without chemical reactions altering the composition. These problems are discussed in detail and it is concluded that only fast reactions, with relaxation times less than 1 μs, are capable of falsifying an ion spectrum. The ions present in combustion plasmas are described. Their kinetics of production by collisional and chemi-ionization processes, and recombination by both two and three-body schemes are measured for various flame compositions and temperatures. In addition, cross-sections are presented for reaction of H2O+ with various atoms and molecules, as wall as for dissociative attachment of electrons to HCl. As examples of thermodynamic information resulting from this type of study, the first hydration energies of a variety of positive ions are measured, as also are the ionization potentials of CaOH and SrOH.