NEGATIVE AND SECONDARY ION FORMATION IN LOWPRESSURE FLAMES.
AEROCHEM RESEARCH LABS INC PRINCETON N J
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Mass spectrometry and Langmuir probes were used in a study of secondary positive and negative ion formation in low-pressure flames. Individual positive and negative ion profiles were examined as a function of pressure and flame composition. The effects of various additives including N2, CO2, CH3OH, CH2O and CH3CHO were also studied in these flames, as well as in a low-pressure atomic diffusion flame. Two mechanisms for secondary positive ion formation are set forth. The first consists of a series of charge exchange reactions involving the primary ion and stable neutral combustion intermediates. The second mechanism is one in which a primary ion undergoes a chain of oxidative degradation reactions which includes the observed ions as intermediates. Addition of N2 and CO2 to combustion flames, together with the observed effects of varying flame stoichiometry, led to the conclusion that, in addition to CHO cation, an important primary ion is C3H3 cation. Mass spectrometric negative ion profiles indicate the presence of significant quantities of negative ions in flames at 1 to 3 Torr. Author