O-2 dissociation in Ar-O-2 surface-wave microwave discharges

• Type: Article in International Scientific Journal
• Date: 2012

Authors

Kutasi, K (Author) Other; P. A . Sá (Author) FEUP; Guerra, V (Author) Other

Journal

Title: Journal of Physics D: Applied Physics

Vol. 45

Final page: 195205

ISSN: 0022-3727

Publisher: Institute of Physics Publishing

Indexing

ISI Web of Knowledge - 11 Citations

ISI Web of Science

Scopus - 14 Citations

Scientific classification

FOS: Natural sciences

Other information

Authenticus ID: P-002-A0K

DOI: 10.1088/0022-3727/45/19/195205

Abstract (EN): A self-consistent model is developed in order to investigate the dissociation of O-2 molecules in Ar-O-2 surface-wave microwave discharges. The dissociation degree of O-2 molecules ([O]/2[O-2](0)) is determined for surface-wave discharges generated in 0.5 cm and 2.8 cm diameter tubes with 2.45 GHz and 915 MHz microwave field frequencies, respectively, in the 0.5-25 mbar pressure range at different mixture compositions from pure O-2 to 95% Ar-5% O-2. The dissociation degree varies non-monotonically with pressure-it passes through a minimum-which is more pronounced in high Ar content mixtures. This behaviour is found to be a consequence of the electron collision processes, in particular the evolution of the non-Maxwellian shape of the electron energy distribution function with pressure. These changes make the electron impact dissociation coefficient follow the same non-monotonic trend with pressure, despite leading to the expected monotonic variation of the ionization rate coefficient. The minimum in dissociation is in correlation with the momentum transfer cross-section profiles of the mixture's components, and occurs approximately at the pressure that satisfies the condition nu(ce) = omega, which explains its dependence on omega.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8