Mobilities of various mass-identified positive and negative ions in helium and argon

The mobilities of the ions CH₃O₂⁺, NO ₊·H₂O, C₂H₂^-, Cl^-, O₂^-, O₃^-, NO ₂^-, CO₃^-, SO₃ ^-, SO₂F^-, SF₅^-, and SF₆^- in helium and O⁺, O⁺, O ₃^-, and CO₃^- in argon have been measured at room temperature with a flow-drift tube. The measurements were obtained over the range 5≤E/N≤120 Td for helium and 5≤E/N≤270 Td for argon (1 Td=10^-17 V-cm²). The E/N dependence of these data fits the general pattern observed previously for a variety of ions in helium and argon, with the exception that the O⁺ mobilities in argon exhibit a rare minimum. Several of the polyatomic ions, notably CH ₃O₂⁺, NO⁺·H₂O, and O₃^-, were observed to break up at elevated E/N.