Metastable dissociation ofAr2+produced by associative ionization

The results of a search for metastable dissociations of ${\mathrm{Ar}}_2$ ${\mathrm{}}^{+}$ produced in an ion source via associative ionization are presented. The metastable fragmentations were studied with a double-focusing mass spectrometer by decoupling the acceleration and analyzer fields. The number of metastable transitions occurring in the observable time window between 3.1 and 7.9 μs after ion formation increases with electron energy in the ion source and is ≊100 times larger than the number of metastable transitions observed previously for ${\mathrm{Ar}}_2$ ${\mathrm{}}^{+}$ produced by electron ionization of ${\mathrm{Ar}}_2$. Decomposition pathways consistent with ab initio potential diagrams are presented.