Sequential deprotonation of the allene trication produced by 30-keV/u He2+ impact

Abstract

The three-body fragmentation channel ${\mathrm{H}}^{+}+{\mathrm{H}}^{+}+{\mathrm{C}}_{3}{\mathrm{H}}_{2}{}^{+}$ of the allene trication produced by 30-keV/u ${\mathrm{He}}^{2+}$ ion impact is investigated using cold-target recoil-ion momentum spectroscopy. The two protons with different kinetic energies are found emitted sequentially from the parent trication. The presence of such a sequential deprotonation process and the absence of corresponding concerted deprotonation may result from a major molecular deformation process, e.g., ultrafast hydrogen migration, which occurs in the parent ion prior to fragmentation, and finally leads to the formation of two different protons.