Reaction rate constants for O−2(H2O)n ions n = 0 to 4, with O3, NO, SO2, and CO2

Reaction rate constants for O−2(H2O)n ions with n = 0 to 4 have been measured in a variable temperature flowing afterglow apparatus with a novel ion source configuration. The ions have been reacted with O3,NO, SO2, and CO2. The reaction with O3 is charge-transfer to produce O−3 with simultaneous transfer of water ligands. The reactions with NO and SO2 are ligand switching reactions in which NO or SO2 displaces one or more water molecules clustered to O−2 leaving NO−3 and SO−4 as core ions. In these cases, the reaction rate constants are not decreased measurably by an increase in n. CO2 rapidly displaces H2O in reaction with O−2(H2O) but does not react with O−2(H2O)3,4. Isotopically labelled O−2 ions were used to elucidate several reaction mechanisms. The rapid destruction of O−2(H2O)4 ions by O3,NO, and SO2 insure that O−2(H2O)n ions cannot be dominant small air ions in the earth’s lower atmosphere.