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The three-body fragmentation dynamics of benzene trications C 6 H 6 3 + induced by 200 eV electron-impact produced by a photoemission cathode is investigated. All three fragment ions are detected in coincidence, and their momentum vectors are determined by employing a COLTRIMS reaction microscope. The detailed kinematical information of three deprotonation fragmentation channels of H+ + C 3 H 2 + + C 3 H 3 + , H+ + C 2 H 3 + + C 4 H 2 + , and H+ + C 2 H 2 + + C 4 H 3 + are obtained. By analyzing the momentum and energy correlation spectra among all the three fragment ions, we find that all the three channels are primarily generated by sequential fragmentation processes. Each channel has two deprotonation pathways, corresponding to proton emission in the first or second step of sequential fragmentation, respectively. These results provide insight into the mechanisms and dynamics of deprotonation and ring-breaking reactions in the three-body fragmentation processes of aromatic ring molecules. [ABSTRACT FROM AUTHOR]

The fragmentation of two isomers of C3H4, propyne (CH3CCH) and allene (CH2CCH2), is investigated by 50 keV/u Ne8+ impact. Obvious isomer effects are observed by comparing the time-of-flight spectra generated from the two isomers. Six two-body fragmentation channels of C3 H 4 2 + dications are identified for each isomer. CH 2 + + C2 H 2 + is found to be the most favored CC bond breaking channel for both isomers, indicating that CH3CCH2+ intends to rearrange to the structure containing the CH2 group before fragmentation. For CH bond breaking channels, it is found that the CH3CCH which contains a CH3 group is more efficient for H 2 + and H 3 + ejection. In addition, two-body dissociation channels of C3 H 4 3 + trications are identified. While the H+ + C 3 H 3 2 + channel is observed in the fragmentation of both isomers, the H 2 + + C 3 H 2 2 + channel only occurs in the fragmentation of CH3CCH3+. For CH2 CCH 2 3 + , the peak and shoulder structures in the kinetic energy release spectrum of the H+ + C 3 H 3 2 + channel are attributed to different geometries of the C 3 H 3 2 + product. [ABSTRACT FROM AUTHOR]

The single ionization and dissociation of ethanol molecules induced by low-energy electrons ( E 0 = 90   eV) are investigated using multiparticle coincident momentum spectroscopy. By detecting two outgoing electrons ( e 1 and e 2 ) and one fragment ion in coincidence, we obtain the energy deposition ( E 0 − E 1 − E 2 ) during electron ionization of the molecule, i.e., the binding energy spectra, for production of the different ionic fragments C2H5OH+, C2H4OH+, COH+, and H3O+. These data allow us to study the ionization channels for different ionic products. In particular, we focus on H3O+ as a product of double hydrogen migration. It is found that this channel mainly originates from the ionization of outer-valance orbitals (3a ″ ,10a ′ , 2a ″ , 9a ′ , 8a ′ , 1a ″ , and 7a ′ ). Additionally, there are minor contributions from the inner-valence orbitals such as 6a ′ , 5a ′ , and 4a ′ . Quantum chemistry calculations show two fragmentation pathways: concerted and sequential processes for formation of H3O+. [ABSTRACT FROM AUTHOR]

The three-body fragmentation dynamics of benzene trications C6H63+ induced by 200 eV electron-impact produced by a photoemission cathode is investigated. All three fragment ions are detected in coincidence, and their momentum vectors are determined by employing a COLTRIMS reaction microscope. The detailed kinematical information of three deprotonation fragmentation channels of H+ + C3H2+ + C3H3+, H+ + C2H3+ + C4H2+, and H+ + C2H2+ + C4H3+ are obtained. By analyzing the momentum and energy correlation spectra among all the three fragment ions, we find that all the three channels are primarily generated by sequential fragmentation processes. Each channel has two deprotonation pathways, corresponding to proton emission in the first or second step of sequential fragmentation, respectively. These results provide insight into the mechanisms and dynamics of deprotonation and ring-breaking reactions in the three-body fragmentation processes of aromatic ring molecules., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

The inner-valence ionization and fragmentation dynamics of CH 4 -C 6 H 6 dimer induced by 200 eV electron impact is studied utilizing a multi-particle coincidence momentum spectroscopy. The three-dimensional momentum vectors and kinetic energy release (KER) of the CH 4 + +C 6 H 6 + ion pairs are obtained by coincident momentum measurement. Our analysis on the absolute cross sections indicates that the intermediate dication CH 4 + -C 6 H 6 + is preferentially produced by the removal of an inner-valence electron from CH 4 or C 6 H 6 and subsequent relaxation of ultrafast intermolecular Coulombic decay followed by two-body Coulomb explosion. Combining with ab initio molecular dynamics (AIMD) simulations, the real-time fragmentation dynamics including translational, vibrational and rotational motions are presented as a function of propagation time. The revealed fragmentation dynamics are expected to have a potential implication for crystal structure imaging with various radiation sources., (© 2023 IOP Publishing Ltd.)

The fragmentation of two isomers of C 3 H 4 , propyne (CH 3 CCH) and allene (CH 2 CCH 2 ), is investigated by 50 keV/u Ne 8+ impact. Obvious isomer effects are observed by comparing the time-of-flight spectra generated from the two isomers. Six two-body fragmentation channels of C 3 H 4     2+ dications are identified for each isomer. CH 2    + + C 2 H 2    + is found to be the most favored CC bond breaking channel for both isomers, indicating that CH 3 CCH 2+ intends to rearrange to the structure containing the CH 2 group before fragmentation. For CH bond breaking channels, it is found that the CH 3 CCH which contains a CH 3 group is more efficient for H 2    + and H 3    + ejection. In addition, two-body dissociation channels of C 3 H 4    3+ trications are identified. While the H + + C 3 H 3    2+ channel is observed in the fragmentation of both isomers, the H 2    + + C 3 H 2    2+ channel only occurs in the fragmentation of CH 3 CCH 3+ . For CH 2 CCH 2    3+ , the peak and shoulder structures in the kinetic energy release spectrum of the H + + C 3 H 3    2+ channel are attributed to different geometries of the C 3 H 3    2+ product.