Nature of charge carriers in negative coronas.
Mass spectrometric studies of ionic species formed in negative corona discharges in air and pure oxygen have been carried out at total pressures ranging from 5 Torr to 760 Torr. In air, the importance of trace amount of carbon dioxide is demonstrated by the dominant presence CO(3)(-) ion at pressures above 50 Torr. This ion comprises over 90% of the total ionic species which reach the anode at atmospheric pressure. At relative humidities of 20-50%, the contributions of the hydrated species such as CO(3)(-)(H(2)O), O(-)(H(2)O), and O(3)(-)(H(2)O)) are less than 10%. In pure oxygen the two important ionic species appear to be O(3)(-) and O(-) with the contribution of the former increasing with pressure. Trace impurities of carbon dioxide in oxygen, however, convert the carriers to CO(3)(-) which makes the dominant contribution to the total current.
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