Ultrafast ring-opening fragmentation dynamics of C6H63+ induced by electron-impact ionization

Abstract

The fragmentation dynamics of triply charged benzene [(${\mathrm{C}}_{6}{\mathrm{H}}_{6}{)}^{3+}$] induced by 260 eV electron-impact ionization are investigated using a multiparticle coincidence momentum spectrometer. By measuring three fragment ions and one outgoing electron in quadruple coincidence, we identify the complete three-body dissociation channels of ${{\mathrm{CH}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{3}}^{+} + {\mathrm{C}}_{3}{\mathrm{H}}^{+}, {{\mathrm{CH}}_{3}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{3}{\mathrm{H}}^{+}$, and ${\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+} + {\mathrm{C}}_{2}{{\mathrm{H}}_{2}}^{+}$. We determine the projectile-energy-loss spectra, Dalitz plots, Newton diagrams, momentum correlation maps, and kinetic-energy release for each fragmentation channel. The analysis of these spectra is supported by an ab initio molecular dynamics simulation, which provides a molecular movie of the dissociation process. Our study reveals sequential mechanisms for all three dissociation channels of (${\mathrm{C}}_{6}{\mathrm{H}}_{6}{)}^{3+}$ trication, i.e., an ultrafast ring-opening reaction followed by two subsequent Coulomb-explosion processes.