THE REACTION SF5- COMPETITION BETWEEN ASSOCIATION AND BINARY REACTIONS(+H2S AT NEAR THERMAL ENERGIES )

The reaction between SF5+ and H2S has been investigated in the energy regime from 0.052 to 1.7 eV, KE(cm), using a selected ion flow drift t ube (SIFDT) operating with helium buffer gas. At low energies a slow b inary reaction channel into SF4HS+ occurs in parallel with a fast asso ciation reaction. Both rate coefficients decline from 3 x 10-(11) cm(3 ) s(-1) and 3 x 10(-27) cm(6) s(-1) respectively at 0.052 eV to < 5 x 10-(12) cm(3) s(-1) and < 5 x 10(-28) cm(6) s(-1) respectively at 0.3 eV, KE(cm). Above 0.3 eV the endoergic charge transfer channel becomes dominant, the rate coefficient increasing to 9 x 10-(12) cm(3) s(-1) at 1.7 eV, KE(cm).SF5+.H2S was found to react fast with H2S, the rate coefficient being 1.4 x 10(-9) cm(3) s(-1).