Negative ion effects in CO2 convection laser discharges

Negative ions are computed to be formed on a time scale and in quantities such that they may be a cause of plasma instability observed in low pressure electrical discharge convection CO₂ lasers. In a typical CO₂?N₂?He?H₂O laser mixture the principal ions are CO ₃ ^? , CO ₄ ^? and H^? with the total negative ion densityn _? given by 0.1n _e <n _?<n _e , wheren _e is the electron density: but if the gases are re-cycled or if there is an air leak NO ₂ ^? and NO ₃ ^? are formed in significant amounts andn _? can become greater thann _e in a time considerably less than the gas dwell time in the electrical excitation discharge. CO is effective in reducingn _? in a system without re-cycling, but is ineffective in a re-cycled system with the oxides of nitrogen present.