The associative ionization of N(²P) + O(³P)

The rate constant of the associative ionization reaction N(P-2) + O(P-3) -> NO+ + e(-) was measured using a flow tube apparatus. A flowing afterglow source was used to produce an ion/electron plasma containing a mixture of ions, including N-2(+), N-3(+), and N-4(+). Dissociative recombination of these species produced a population of nitrogen atoms, including N(P-2). Charged species were rejected from the flow tube using an electrostatic grid, subsequent to which oxygen atoms were introduced, produced either using a discharge of helium and oxygen or via the titration of nitrogen atoms with NO. Only the title reaction can produce the NO+ observed after the introduction of O atoms. The resulting rate constant (8 +/- 5 x10(-11) cm(3) s(-1)) is larger than previously reported N(P-2) + O disappearance rate constants (similar to 2 x 10(-11) cm(3) s(-1)). The possible errors in this or previous experiments are discussed. It is concluded that the N(P-2) + O(P-3) reaction proceeds almost entirely by associative ionization, with quenching to the D-2 or S-4 states as only minor processes.