REACTIONS OF SF6- AND I- WITH ATMOSPHERIC TRACE GASES

The rate constants for the reactions of SF6- with ClNO3, HNO3, HCl, N2 O5, NO2, O-3, Cl-2, Cl2O, HOCl, CF2O, CF3CFO, and SO2 were measured at 293 K using the flowing afterglow technique. The rate coefficients ra nge from 2 x 10(-11) to 2 x 10(-9) cm(3) molecule(-1) s(-1) Most of th e SF6- reactions give multiple products except for Cl-2, NO2, and O-3, which react only by charge transfer, and CF2O and CF3CFO, which react only by fluoride transfer. The reactions of SF6- with Br2O, BrNO3, an d HOBr were studied qualitatively. All of the SF6- reactions studied p rovide a method for selectively detecting the neutral reactant by chem ical ionization mass spectrometry. The reactions of I- with CINO3, N2O 5, HNO3, NO2, and O-3 were also studied. The reactions with CINO3 and N2O5 are fast (kappa greater than or equal to 9 x 10(-10) cm(3) molecu le(-1) s(-1)) and produce only NO3-. I- is unreactive with HNO3, NO2, and O-3. The SF6- reactions with HCl and O-3 and the I- reaction with N2O5 were found to be significantly faster than reported previously.