Associative ionization of N(2D) and O

Abstract Recent laboratory measurements have shown that N( 2 P) atoms, and thus probably hot N( 2 D) atoms, will recombine with atomic oxygen via an associative ionization process at the gas kinetic rate. While the reaction is endothermic, it has been suggested that this has interesting implications for the upper atmosphere in that N( 2 D) atoms in the tail of the velocity distribution could provide an additional source of NO + through the reverse of the dissociative recombination reaction NO + + e ⇄ N ( 2 D ) + O . It has also been suggested that this process might account for the difference between a laboratory determination of the rate coefficient and that determined from the Atmospheric Explorer Satellite data. In this paper we investigate further the likelihood of the associative ionization of N( 2 D) and O playing a significant role in the normal ionosphere, in the light of several recent relevant studies. We conclude that the associative ionization process is not an important factor and that a more probable cause for disagreements in the various determinations of the recombination coefficient, is the difference in excited states of the ions in the various experiments.