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

We describe a volume averaged global model for an inductively coupled RF oxygen discharge that considers an extensive reaction set that includes the species: O-2(X-3 Sigma(-)(g)), O-2(a(1)Delta(g)), O-2(b(1)Sigma(+)(g)), O-2(A(3)Sigma(+)(u), A('3)Delta u, c(1)Sigma(-)(u)), O-2(+), O-2(-), O(P-3), O(D-1), O+, O-, O-3, O-3(+), O-3(-), 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 O-2(a(1)Delta(g)) density can be lower than the O-2(b(1)Sigma(+)(g)) density in the pressure range from 2.5 to 80 mTorr. The relative reaction rates for formation and annihilation of O-2(a(1)Delta(g)) and O-2(b(1)Sigma(+)(g)) are evaluated and the most important reactions are indicated. The O- loss process is also studied. The results show that O-2(a(1)Delta(g)) 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(P-3) and the metastable singlet O-2(b(1)Sigma(+)(g)) are the most effective loss process up to roughly 50 mTorr where charge exchange becomes the most effective process for O- loss. (AU)