The reactivity, energetics and dynamics of the bimolecular reactions between Ar2+ and O2 have been
studied using a position sensitive coincidence methodology at a collision energy of 4.4 eV. Four
bimolecular reaction channels generating pairs of product ions are observed, forming: Ar+ + O2
+, Ar+ + O+,
ArO+ + O+ and O+ + O+. The formation of Ar+ + O2
+ is a minor channel, involving forward scattering, and
generates O2
+ in its ground electronic state. This single electron transfer process is expected to be facile by
Landau–Zener arguments, but the intensity of this channel is low because the electron transfer pathways
involve multi-electron processes. The formation of Ar+ + O+ + O, is the most intense channel following
interactions of Ar2+ with O2, in agreement with previous experiments. Many different combinations of Ar2+
and product electronic states contribute to the product flux in this channel. Major dissociation pathways of
the nascent O2
+
* ion involve the ion’s first and second dissociation limits. Unusually, the experimental results
clearly show the involvement of a short-lived collision complex [ArO2]
2+ in this channel. The formation of O+
and ArO+ involves direct abstraction of O from O2 by Ar2+. There is scant evidence of the involvement of a
collision complex in this bond forming pathway. The ArO+ product appears to be formed in the first
excited electronic state (2
P). The formation of O+ + O+ results from dissociative double electron
transfer via an O2
2+ intermediate. The exoergicity of the dissociation of the nascent O2
2+ intermediate is
in good agreement with previous work investigating the unimolecular dissociation of this dication
