The role of O2(a1Δg) metastables and associative detachment in discharges in oxygen

A model of discharges in oxygen is developed which takes into consideration the role that the long-lived metastable state O 2 (a 1 Δ g ) can play in their dynamics. This enables the electron temperature ( T e ) versus pressure × plasma dimension ( pL ) characteristic to be found over the range 1 mTorr cm to 1 Torr cm. The conclusion is reached that only at the very low pressure end and high electron densities is oxygen a recombination-dominated gas and that generally at higher pressures it is detachment dominated . In between, both recombination and detachment are important to describe the loss of negative ions. The paper brings together two separate approaches to discharges in oxygen and demonstrates that each has its own place, while at the same time making it clear that oxygen is a special case rather than an exemplar for electronegative gases in general.