The three-body fragmentation dynamics of propene trications $\left[{({\mathrm{H}}_3\mathrm{C}–\mathrm{CH}={\mathrm{CH}}_2)}^{3+}\right]$ induced by 1-MeV/u ${\mathrm{C}}^{4+}$ ion impact is investigated using cold-target recoil-ion momentum spectroscopy. Complete kinematical information is obtained for four three-body fragmentation channels: ${\mathrm{H}}^{+}+{\mathrm{CH}}_2{}^{+}+{\mathrm{C}}_2{\mathrm{H}}_3{}^{+}, {\mathrm{H}}^{+}+{\mathrm{CH}}_3{}^{+}+{\mathrm{C}}_2{\mathrm{H}}_2{}^{+}$, and the channels involving ${\mathrm{H}}_2{}^{+}$ production, i.e., ${\mathrm{H}}^{+}+{\mathrm{H}}_2{}^{+}+{\mathrm{C}}_3{\mathrm{H}}_3{}^{+}$ and ${\mathrm{H}}_2{}^{+}+{\mathrm{CH}}_2{}^{+}+{\mathrm{C}}_2{\mathrm{H}}_2{}^{+}$. By analyzing the fragment momentum correlations visualized in Dalitz plots, Newton diagrams, and native frames, each channel exhibits two distinct sequential processes, with a concerted process uniquely identified in the ${\mathrm{H}}_2{}^{+}+{\mathrm{CH}}_2{}^{+}+{\mathrm{C}}_2{\mathrm{H}}_2{}^{+}$ channel. Relative contributions of competing fragmentation pathways are determined. The sequential pathways with CH breakage prior to CC breakage predominate in the channels ${\mathrm{H}}^{+}+{\mathrm{CH}}_2{}^{+}+{\mathrm{C}}_2{\mathrm{H}}_3{}^{+}$ and ${\mathrm{H}}^{+}+{\mathrm{CH}}_3{}^{+}+{\mathrm{C}}_2{\mathrm{H}}_2{}^{+}$. Due to comparable timescales, the ${\mathrm{H}}_2$ formation kinetically competes with the molecular fragmentation. This competition enables fragmentation pathways featuring initial ${\mathrm{H}}_2{}^{+}$ emission, which contribute to two ${\mathrm{H}}_2{}^{+}$ production channels. This study provides valuable insights into understanding the dissociation behaviors of asymmetric hydrocarbon chains under several-MeV/u ion impact, revealing the role of ${\mathrm{H}}_2$ formation kinetics in molecular fragmentation dynamics.

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• Atomic & molecular collisions