On the formation and annihilation of the singlet molecular metastables in an oxygen discharge

Abstract

We describe a volume averaged global model for an inductively coupled RF oxygen discharge that considers an extensive reaction set that includes the species: O2(X), O2(), O2(), O2(A, A’, ), O, O, O(3P), O(1D), O+, O−, O3, O, O, and electrons. We propose revised rate coefficients for some of the reactions and explore the densities of various species as a function of discharge pressure, in the pressure range 1–100 mTorr. We find that the O2() density can be lower than the O2() density in the pressure range from 2.5 to 80 mTorr. The relative reaction rates for formation and annihilation of O2() and O2() are evaluated and the most important reactions are indicated. The O− loss process is also studied. The results show that O2() has only a small contribution to the loss of the negative ion O−, while electron impact detachment is a very effective loss process at low pressure (<2 mTorr) and detachment by the oxygen atom O(3P) and the metastable singlet O2() are the most effective loss process up to roughly 50 mTorr where charge exchange becomes the most effective process for O− loss.