Identification of corona discharge-induced SF6 oxidation mechanisms using SF6/18O2/H2 16O and SF6/16O2/H2 18O gas mixtures

Abstract

The absolute yields of gaseous oxyfluorides SOF/sub 2/, SO/sub 2/F/sub 2/, and SOF/sub 4/ from negative, point-plane corona discharges in pressurized gas mixtures of SF/sub 6/ with O/sub 2/ and H/sub 2/O enriched with /sup 18/O/sub 2/ and H/sub 2/ /sup 18/O have been measured using a gas chromatograph-mass spectrometer. The predominant SF/sub 6/ oxidation mechanisms have been revealed from a determination of the relative /sup 18/O and /sup 16/O isotope content of the observed oxy-fluoride by-products. The results are consistent with previously proposed production mechanisms and indicate that SOF/sub 2/ and SO/sub 2/F/sub 2/ derive oxygen predominantly from H/sub 2/O and O/sub 2/, respectively, in slow, gas-phase reactions involving SF/sub 4/, SF/sub 3/, and SF/sub 2/ that occur outside of the discharge region. The species SOF/sub 4/ derives oxygen from both H/sub 2/O and O/sub 2/ through fast reactions in the active discharge region involving free radicals or ions such as OH and O, with SF/sub 5/ and SF/sub 4/.