Double collision experiments

A variety of double collision experiments, whereby fast species undergo collisional interactions in two distinct regions of a mass spectrometer, are described. These include two‐stage charge reversal of negative ions, two‐stage double electron transfer from targets to cations, neutralization‐reionization experiments as well as delayed analysis of organic cations formed in a one‐step charge reversal of anions. Experiments have been performed on a number of systems of current interest in gas‐phase ion chemistry. It is concluded that autoelectron detachment of benzyl anions leads to benzyl radicals, whereas the collisionally induced electron detachment produces a mixture of benzyl and tropyl radicals. By contrast, electron detachment from [H 3 CNH] − is not a metastable process and occurs only after excitation to produce H 3 CNH˙ radicals, which do not rearrange into the thermodynamically more stable H 2 CNH 2 ˙. It is shown that in the double electron transfer reactions H + + Xe→H˙ + Xe + ˙ and H˙ + Xe→H − + Xe + ˙, excited states are produced. From double collision experiments on methyl formate ions, it is concluded that the non‐decomposing ions have undergone rearrangement on the time‐scale of 10 μs into the distonic isomer, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm H} - \mathop {\rm C}\limits^ + ({\rm OH}){\rm O}\mathop {\rm C}\limits^. {\rm H}_2 $\end{document} . Finally, it is shown that short‐lived (<0.2 μs) [H 2 , C, N] + ions generated by charge‐reversal of [H 2 CN] − have the [H 2 CN] + structure, whereas most of the long‐lived (10 μs) ions have the [HCNH] + structure.