Abstract
Ionisation processes in the He-CO and He-CO-O2 glow discharges are studied. Various models are critically reviewed and an alternative ionisation mechanism is proposed. The populations of the CO and O2 metastable levels and the rates of direct and step ionisation processes are calculated. It is argued that the metastable level of CO can be efficiently populated by energy transfer due to collisions between vibrationally excited molecules. It is shown that the direct ionisation of CO in the H-CO discharge is replaced by step ionisation of O2 in the He-CO-O2 discharge. This explains both the reduced axial electric field and the fact that O2+ is the dominant ion in the He-CO-O2 discharge.

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