Negative Oxygen Ion Formation in a Pulsed Inductively RF Excited Argon-Oxygen Discharge and the Influence of Highly Excited Oxygen Molecules
Abstract
The temporal behavior of negative oxygen ions oxygen / argon mixtures was investigated in the afterglow of a pulsed inductively excited modified GEC reactor. The objective of this investigation is an improved understanding of the production reactions of the negative ions and the loss processes of negative ions during the plasma decay phase. Collisions of O-minus ions with O atoms and metastable oxygen molecules lead to considerable electron production in the afterglow. This late supply of electrons entails a delayed formation of a so-called ion-ion plasma. Discharges with admixtures of argon (up to 8:2 argon : oxygen) are also strongly electronegative. An increase of the absolute O-minus density is observed with increasing argon fraction. At low pressures and high contents of argon it is necessary to consider an additional production reaction channel for the negative ions in order to explain the measured increase of the negative ion density. Appearance potential mass spectroscopy measurements show an increase of highly excited oxygen molecules with increasing argon fraction. It is, therefore, likely that additional negative ions are generated by dissociative attachment of highly excited metastable oxygen molecules [1]. [1] D. Hayashi and K. Kadota, J. Appl. Phys. 83 (1998) 697 This project is funded by the Bundesminister für Bildung und Forschung BMBF (FKZ 13N8052).
- Publication:
-
APS Annual Gaseous Electronics Meeting Abstracts
- Pub Date:
- October 2003
- Bibcode:
- 2003APS..GECNWP063K