Oxygen discharges diluted with argon : dissociation processes

• We use a global (volume averaged) model to study the dissociationprocesses and the presence of negative ions and metastable species in a lowpressure high density O2/Ar discharge in the pressure range 1–100 mTorr.The electron density and the fractional dissociation of the oxygen moleculeincreases with increased argon content in the discharge. We relate thisincrease in fractional dissociation to an increase in the reaction rate forelectron impact dissociation of the oxygen molecule which is due to theincreased electron temperature with increased argon content in thedischarge. The electron temperature increases due to higher ionizationpotential of argon than for molecular and atomic oxygen. We find thecontribution of dissociation by quenching of the argon metastable Armbymolecular oxygen (Penning dissociation) to the creation of atomic oxygen tobe negligible. The negative oxygen ion O−is found to be the dominantnegative ion in the discharge. Dissociative attachment of the oxygenmolecule in the ground state O2(X3−g)and in particular the metastableoxygen molecule O2(a1g)are the dominating channels for creation of thenegative oxygen ion O−.(Some figures in this article are in colour only in the electronic version)

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NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

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