Fragmentation dynamics of acetylene in collision with highly charged ions: Concerted and sequential breakage of CH and CC bonds

The three-body fragmentation of C2H23+ to H+ + C+ + CH+ as a consequence of one CH and one CC bond breaking is investigated by 50-keV/u Ne8+ impact. All three fragments are detected in coincidence with a scattered projectile (either Ne7+ or Ne6+) employing a reaction microscope, and their momentum vectors as well as the kinetic energies were obtained. Four distinguished structures are observed in the energy correlation spectra, indicating that abundant fragmentation mechanisms contribute to the H+ + C+ + CH+ channel. The Newton diagrams and Dalitz plots are employed to trace fragmentation mechanisms. We found that both the concerted fragmentation and the sequential pathway with CH bond breaking prior to CC contribute to this channel. The possible electronic states of the C2H23+ precursor that may contribute to the identified fragmentation mechanisms are analyzed with the help of quantum chemical calculations. Furthermore, the influence of the collision dynamics between the projectile and the target to the dissociation mechanisms is discussed by comparing the contributions from the reaction channel with transferring one electron while ionizing the other two, i.e., T1I2, and the reversed channel T2I1. The T2I1 channel is observed to be more efficient to initiate fragmentation mechanisms leading to higher kinetic-energy release.

Automated summary

The three-body fragmentation of C2H23+ to H+ + C+ + CH+ resulting from CH and CC bond breaking is studied under 50-keV/u Ne8+ impact. All three fragments are detected in coincidence with a scattered projectile (either Ne7+ or Ne6+) using a reaction microscope, and their momentum vectors and kinetic energies are obtained. Four distinct structures are observed in the energy correlation spectra, indicating multiple fragmentation mechanisms contributing to the H+ + C+ + CH+ channel. Newton diagrams and Dalitz plots are used to trace these fragmentation mechanisms. It is found that both concerted fragmentation and sequential pathways involving CH bond breaking prior to CC contribute to this channel. The possible electronic states of the C2H23+ precursor that contribute to the identified fragmentation mechanisms are analyzed using quantum chemical calculations. Furthermore, the influence of collision dynamics between the projectile and target on the dissociation mechanisms is discussed by comparing the contributions from the T1I2 channel and the reversed T2I1 channel, where one electron is transferred while ionizing the other two. The T2I1 channel is observed to be more efficient in initiating fragmentation mechanisms with higher kinetic energy release.