Dissociation mechanism of C2H42+ induced by 18-keV/u Ne8+ impact: Symmetric and isomeric cleavage of the C-C bond

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The C-C bond cleavage dissociation of ethylene dication produced by 18-keV/u ${\mathrm{Ne}}^{8+}$ impact is investigated by combining experimental measurement and theoretical calculation. Using cold target recoil ion momentum spectroscopy, two channels, i.e., the symmetric fragmentation, ${\mathrm{C}}_{2}\mathrm{H}{{}_{4}}^{2+} \ensuremath{\rightarrow} \mathrm{C}\mathrm{H}{{}_{2}}^{+}+\mathrm{C}\mathrm{H}{{}_{2}}^{+}$, and the isomeric one, ${\mathrm{C}}_{2}\mathrm{H}{{}_{4}}^{2+} \ensuremath{\rightarrow} \mathrm{C}{\mathrm{H}}^{+}+\mathrm{C}\mathrm{H}{{}_{3}}^{+}$, are clearly identified and thus their kinetic-energy release (KER) distributions are determined. The average KER values are then compared with the theoretical results obtained by quantum chemical calculations, which provide reaction paths of both channels on the potential-energy surfaces of different molecular states. It is found that the hydrogen transfer process and excited-state dynamics still play crucial roles in the formation of C-C bond cleavage channels, but in a different way in comparison with the cases of acetylene ${\mathrm{C}}_{2}{\mathrm{H}}_{2}$ and ethane ${\mathrm{C}}_{2}{\mathrm{H}}_{6}$.