Transfer of F- in the reaction of SF6- with SOF4: Implications for SOF4 production in corona discharges

Abstract

The temperature (T) and electric field-to-gas pressure (E/P) dependences of the rate coefficientk for the reaction SF 6 � +SOF4rarrSOF 5 � +SF5 have been measured. ForT<270>k approaches a constant of 2.1×10�9 cm3/s, and for 433>T>270 K,k decreases withT according tok (cm3/s)=0.124 exp [�3.3 lnT(K)]. ForE/Pk has a constant value of about 2.5×10�10 cm3/s, and for 130 V/cm·torr>E/P>60 V/cm·torr, the rate is approximately given byk (cm3/s)sim7.0×10�10 exp (�0.022E/P). The measured rate coefficient is used to estimate the influence of this reaction on SOF4 production from negative, point-plane, glow-type corona discharges in gas mixtures containing SF6 and at least trace amounts of O2 and H2O. A chemical kinetics model of the ion-drift region in the discharge gap is used to fit experimental data on SOF4 yields assuming that the SF 6 � +SOF4 reaction is the predominant SOF4 loss mechanism. It is found that the contribution of this reaction to SOF4 destruction falls considerably below the estimated maximum effect assuming that SF 6 � is the predominant charge carrier which reacts only with SOF4. The results of this analysis suggest that SF 6 � is efficiently deactivated by other reactions, and the influence of SF 6 � +SOF4 on SOF4 production is not necessarily more significant than that of other slower secondary processes such as gas-phase hydrolysi