Positive and negative ion reactions in carbon dioxide

The positive and negative ions produced in carbon dioxide over a wide range of E/N have been examined in a drift tube/mass spectrometer experiment. The positive ion spectra show that unless considerable care is taken to maintain high purity of the gas samples, the dominant ion species are H + (H 2 O) n and to a lesser extent HCO 2 + . The spectra are interpreted on the basis of the formation of H 2 CO 3 through chemisorption of CO 2 at surfaces in the gas inlet line. For pure CO 2 the dominant ions were O 2 + and CO 2 + . The charge exchange reaction O 2 + +CO 2 to CO 2 + +O 2 was observed at E/N>or approximately=135 Td and values of its reaction rate are reported for 135<E/N<390 Td.