Laboratory measurements of the O⁺(²D) + N₂ and O⁺(²D) + O₂ reaction rate coefficients and their ionospheric implications

Rate coefficients have been measured at thermal energies for the charge transfer reactions of metastable O + (²D) ions with N 2 and O 2 . At an effective temperature of ∼ 550 K we find k(N 2 ) = (8 ± 2) × 10 −10 cm³/sec and k(O 2 ) = (7±2) × 10 −10 cm³/sec. These drift tube‐mass spectrometer measurements employ the reaction He + + O 2 as the source of the metastable O + ions, and evidence is presented that the ions thus produced are in the ²D state rather than the ²P state, a possible alternative identification. The O + (²D) + N 2 charge transfer rate is considerably larger than that deduced in existing photochemical model analyses of Atmosphere Explorer observations. Some of the ionospheric implications of the laboratory measurements are discussed.