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 ), O 2 ( ), O 2 ( ), O 2 (A , A’ , ), O , O , O( 3 P), O( 1 D), O + , O − , O 3 , 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 O 2 ( ) density can be lower than the O 2 ( ) density in the pressure range from 2.5 to 80 mTorr. The relative reaction rates for formation and annihilation of O 2 ( ) and O 2 ( ) are evaluated and the most important reactions are indicated. The O − loss process is also studied. The results show that O 2 ( ) 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( 3 P) and the metastable singlet O 2 ( ) are the most effective loss process up to roughly 50 mTorr where charge exchange becomes the most effective process for O − loss.