CHEMISTRY OF ATMOSPHERIC IONS REACTING WITH FULLY FLUORINATED COMPOUNDS

Reactions of the atmospheric ions O+, O-2(+), O-, O-2(-), NO+, H3O+, C O3-, and NO3- with five fully fluorinated compounds were studied using the selected-ion flow tube (SIFT) technique at 300 K. Reaction rate c onstants and product branching fractions were measured for the followi ng selected perfluoro compounds: CF4, C2F6, c-C4F8, n-C6F14, and SF6. The ion O+ reacted at the collisional rate with all five compounds, wi th the oxygen always being a part of the neutral products. The O-2(+) ion reacted with c-C4F8 at unit efficiency and with n-C6F14 at 39% eff iciency, with no oxygen incorporation in the ionic products in either case. The reactions of O- with c-C4F8 and n-C6F14 proceeded at or near unit efficiency, featuring ten and eight product channels, respective ly, including a component from reactive electron detachment in the c-C 4F8 case. In both cases, many of the product channels appeared to be p aired, that is, two channels differing only in the location of the neg ative charge. The reaction of O-2(-) with c-C4F8 proceeded with 37% ef ficiency via non-dissociative charge transfer. The ions NO+, H3O+, CO3 -, and NO3- were unreactive with all five perfluorinated compounds und er investigation.