Production d'atomes métastables O ( 5S) dans un plasma d'oxygène induit par microondes

Abstract

The production of O ( 5 S) metastable oxygen atoms in a microwave induced plasma is studied. The density of metaslable atoms is measured by atomic absorption in the pressure range of 0.2 to 15 torr. Oxygen dilution by noble gases (He, Ar, and Kr) produces a variation of the steady-state concentration of the metastable atoms providing a monitoring technique to control O ( 5 S) concentration at constant flow, pressure and microwave power. The maximum O ( 5 S) concentration measured amounts to 1.8 × 10 11 cm −3 when helium is used as diluant at 4 torr and for a 10% O 2-90% He mixture whereas a typical concentration in pure oxygen at the same pressure is lower than 2 × 10 10 cm −3. A qualitative analysis of the results shows that the electron temperature seems to play a more important role in the O ( 5 S) formation rate than the electron density does.