Factors influencing iron excitation in nitrogen/rare gas microwave plasmas

Abstract The results of experiments involving the use of a microwave-induced plasma operating at atmospheric pressure are discussed. The plasma gases range from pure argon, helium or nitrogen, to mixtures of rare gas and nitrogen. When nitrogen is present, the excitation mechanisms can change dramatically due to the influence of metastable nitrogen molecules. The evidence indicates that nitrogen metastables become important when the nitrogen concentration in the plasma exceeds 3%. Further, data shows that the vibrational states of the nitrogen molecules involved in the excitation process are very important, and can be justified on the basis of Franck-Condon factors.