Electron production through the associative detachment reaction of nitrogen molecules with the negative ion of atomic oxygen revisited in the context of initiation of sprite streamers

Although molecular oxygen, O₂, is an attaching gas, current growth measurements in air demonstrate negligible electron attachment [e.g., Moruzzi and Price, J. Phys. D: Appl. Phys., 7, 1434, 1974]. This observation is interpreted in terms of an electron detachment mechanism involving O^- ions and excited molecular nitrogen, N₂, since detachment of electrons from O^- ions by collision with unexcited O₂ and N₂ molecules practically does not occur at low gas temperatures [e.g., Fehsenfeld et al., J. Chem. Phys., 45, 1844, 1966; Moruzzi et al., J. Chem. Phys., 48(7), 3070, 1968; Kossyi et al., PSST, 1, 207, 1992]. It has been demonstrated that for the associative detachment reaction to proceed, N₂ must be excited to at least the first vibrational level [Hopper et al., J. Chem. Phys., 65, 5474, 1976]. Contrary to studies above and based on a unique flow-drift tube setup, Rayment et al. [Int. J. Mass Spectrom. Ion Phys., 26, 321, 1978] argued that ground state N₂ is in fact responsible for the associative detachment reaction. We note that Doussot et al. [J. Phys. D: Appl. Phys., 15, 2451, 1982] also arrive at the same conclusion with rates in qualitative agreement with those presented in [Rayment et al., 1978], though the O₂/N₂ ratio is significantly different in the two works. Also, it is not obvious how excited species are identified or removed from the drift region to limit the study to O^- reacting with ground state N₂. Here, we review the unique flow-drift tube setup in [Rayment et al., 1978] as it's the only work which provides values for the detachment rate coefficient in a considerable range of reduced electric fields, and is the basis of recent studies devoted to initiation of sprite streamers [e.g., Luque et al., Nat. Geosci., 5, 22, 2012]. In particular, we (i) demonstrate that excited N₂ species in fact do contaminate the experimental setup of [Rayment et al., 1978], (ii) model the experimental setup of [Rayment et al., 1978] using a Green's function method and provide corrections to the approach outlined in that work, and (iii) underscore that reaction rates in majority of flow-drift tube setups mentioned above are obtained under steady state conditions which are not reflective of the transient nature of gas discharge dynamics [e.g., da Silva and Pasko, JGR, 118, 13561, 2013].