The course of the reaction of electronically and vibronically excited metastable O2+(4Πu, ν′) ions with O2, known to produce O3+, was examined by the joint application of computational and mass spectrometric methods. The results show that the reaction does not proceed by a direct mechanism and that it involves instead the intermediacy of the [O2+(4Πu)⋅⋅⋅O2] and [O3+(4A2)⋅⋅⋅O] complexes, both theoretically characterized, and the latter one positively identified by structurally diagnostic mass spectrometric techniques. The reaction is a potential source of stratospheric ozone, in that O3+ ions are known to undergo efficient charge exchange with oxygen to yield neutral O3.