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Pathways of two-body fragmentation of BrCNq+ (q = 2, 3) have been explored by combined experimental and theoretical studies. In the experiment, the BrCN molecule is ionized by 1 keV electron impact and the created fragment ions are detected using an ion momentum imaging spectrometer. Six two-body fragmentation channels are identified. By measuring the momentum vectors of the fragment ions, the kinetic energy release (KER) distributions for these channels have been determined. Theoretically, the potential energy curves of BrCNq+ (q = 2, 3) as a function of Br–C and C–N internuclear distances are calculated by the complete active space self-consistent field method. By comparing the measured KER and theoretical predictions, pathways for the fragmentation channels are assigned. The relative branching ratios of the channels are also determined. [ABSTRACT FROM AUTHOR]

We report an investigation on the fragmentation dynamics of SO2q+ (q = 2–4) induced by 1 keV electron collision utilizing an ion momentum imaging spectrometer. Six complete Coulomb explosion channels were observed using the time-of-flight correlation map. The kinetic energy release distributions for these channels were obtained and compared with those available in the literature. The fragmentation mechanisms of the three-body dissociation channels were analyzed by the Dalitz plots and Newton diagrams. Both concerted breakup and sequential fragmentation pathways were identified in the channel SO23+ → O+ + O+ + S+, whereas only the concerted breakup mechanism was confirmed for the channels SO24+ → O+ + O+ + S2+ and SO24+ → O2+ + O+ + S+. Using the Coulomb explosion model, we determined the molecular geometry from the concerted fragmentation channels, and the obtained bond lengths and angles from the higher kinetic energy release peaks are close to that of the neutral SO2 obtained by high-level quantum chemical calculation. The present results indicate that the electron impact experiment is a potential tool for the Coulomb explosion imaging of small molecules. [ABSTRACT FROM AUTHOR]

The fragmentation dynamics of nitrogen trifluoride (NF3) in collisions with a 500 eV electron is studied by using a momentum imaging spectrometer. The kinetic energy releases of two-body, three-body, and four-body fragmentation channels of N F 3 q + (q = 2, 3) are investigated. The fragmentation dynamics of three-body, as well as four-body, dissociation channels is analyzed by the Dalitz plot and the Newton diagram. It is found that for all of the dissociation channels, the fragment including N atom (ion) always shares significant momenta, regardless of whether it is charged. For F atom, however, it is always emitted with negligible momenta. [ABSTRACT FROM AUTHOR]

The dissociation dynamics of CS2 molecules in collisions with 1.0 keV electrons is studied. We observe a series of two- and three-body fragmentation channels which are identified from the correlation map between fragment ions. For all of the channels, the kinetic energy release (KER) distributions are obtained. The Dalitz plot and Newton diagram are adopted to analyze the fragmentation dynamics of the three-body dissociation channels. For C S 2 3 + and C S 2 4 + , both the concerted and sequential fragmentation mechanisms are observed where the concerted mechanism dominates. For C S 2 5 + , only the concerted mechanism is observed. Two types of Coulomb explosion models considering the molecular vibration are adopted to simulate the experimental KER distributions of the three-body channels. While obvious deviations are observed considering each ion during the whole dissociation process with an integer charge, good agreement can be achieved within deviation less than 5% if the charge state of the ions are adopted from ab initio calculations. [ABSTRACT FROM AUTHOR]

The extensive study of outer- and inner-valence satellites of carbon dioxide by electron momentum spectroscopy is reported. The experiments have been performed using a high-sensitivity electron momentum spectrometer employing non-coplanar symmetric geometry at impact energy of about 1200 eV. Binding energy spectrum up to 50 eV, above the first double ionization threshold (∼37.3 eV), is presented. Four main peaks and twelve satellites have been identified including four embedded in the double ionization continuum, among which the two beyond 42 eV are observed for the first time. High accuracy symmetry-adapted-cluster configuration interaction general-R calculation with aug-cc-pVTZ basis sets has also been performed and the result is in line with the experimental ionization spectrum except the relative intensities for some of the satellites in inner-valence region. The experimental momentum profiles for both the main ionization transitions and satellites have been obtained and compared with theoretical calculations by HF and B3LYP methods with 6-311++G* and aug-cc-pVTZ basis sets. Through comparison, the detailed assignments of the satellite bands have been achieved and the pole strengths for the relevant shake-up transitions are determined experimentally for the first time. [ABSTRACT FROM AUTHOR]

The binding energy spectrum of carbon disulphide (CS2) in the energy range of 9-23 eV has been measured by a high-resolution (e,2e) spectrometer employing asymmetric noncoplanar kinematics at an impact energy of 2500 eV plus the binding energy. Taking the advantage of the high energy resolution of 0.54 eV, four main peaks and five satellites in the outer-valence region are resolved. The assignments and pole strengths for these satellite states are achieved by comparing the experimental electron momentum profiles with the corresponding theoretical ones calculated using Hartree-Fock and density functional theory methods. The results are also compared in detail with the recent SAC-CI general-R calculations. General agreement is satisfactory, while the present experiment suggests cooperative contributions from 2Πu, 2Σg+ states to satellite 2 and 2Σg+, 2Πg states to satellite 3. Besides, relatively low pole strength for X 2Πg state is obtained which contradicts all the theoretical calculations [2ph-TDA, ADC(3), SAC-CI general-R, ADC(4)] so far. [ABSTRACT FROM AUTHOR]

On account of controversial orbital assignment that appeared in previous works, [J. Chem. Phys. 120, 7933 (2004), and references therein] high resolution electron momentum spectroscopy (EMS) measurements on dichlorodifluoromethane has been carried out using a newly developed high resolution energy-momentum dispersive multichannel spectrometer employing asymmetric noncoplanar geometry at an impact energy of 2500 eV plus binding energy. Four resolved structures and two shoulders were obviously observed in high resolution binding energy spectrum in energy range covering eight outermost valence orbitals, whereas only two broad lobes were resolved in previous EMS studies [J. Chem. Phys. 120, 7933 (2004); Chin. Phys. 14, 2467 (2005)]. The ordering of these orbitals was reassigned unambiguously by simple comparison of experimental momentum distributions with theoretical ones. [ABSTRACT FROM AUTHOR]

Electron momentum distributions for outer valence orbitals of CF2Cl2 have been obtained by (e,2e) electron momentum spectroscopy at an incident energy of 1200 eV+binding energy. The experimental electron momentum profiles are compared with Hartree–Fock and density functional theory (DFT) calculations using B3LYP hybrid functional with the 6-31G and 6-311+G* basis sets. Generally, the shapes of the experimental momentum profiles are well reproduced by DFT calculations using larger basis sets 6-311+G*. An attempt has been made to clarify the ordering of the outer valence orbitals, which have been in controversy, by comparing experimental results with B3LYP/6-311+G* calculations. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Pathways of two-body fragmentation of BrCNq+ (q = 2, 3) have been explored by combined experimental and theoretical studies. In the experiment, the BrCN molecule is ionized by 1 keV electron impact and the created fragment ions are detected using an ion momentum imaging spectrometer. Six two-body fragmentation channels are identified. By measuring the momentum vectors of the fragment ions, the kinetic energy release (KER) distributions for these channels have been determined. Theoretically, the potential energy curves of BrCNq+ (q = 2, 3) as a function of Br-C and C-N internuclear distances are calculated by the complete active space self-consistent field method. By comparing the measured KER and theoretical predictions, pathways for the fragmentation channels are assigned. The relative branching ratios of the channels are also determined., (© 2023 Author(s). Published under an exclusive license by AIP Publishing.)

We report an investigation on the fragmentation dynamics of SO 2 q+ (q = 2-4) induced by 1 keV electron collision utilizing an ion momentum imaging spectrometer. Six complete Coulomb explosion channels were observed using the time-of-flight correlation map. The kinetic energy release distributions for these channels were obtained and compared with those available in the literature. The fragmentation mechanisms of the three-body dissociation channels were analyzed by the Dalitz plots and Newton diagrams. Both concerted breakup and sequential fragmentation pathways were identified in the channel SO 2 3+ → O + + O + + S + , whereas only the concerted breakup mechanism was confirmed for the channels SO 2 4+ → O + + O + + S 2+ and SO 2 4+ → O 2+ + O + + S + . Using the Coulomb explosion model, we determined the molecular geometry from the concerted fragmentation channels, and the obtained bond lengths and angles from the higher kinetic energy release peaks are close to that of the neutral SO 2 obtained by high-level quantum chemical calculation. The present results indicate that the electron impact experiment is a potential tool for the Coulomb explosion imaging of small molecules.

The dissociation dynamics of CS 2 molecules in collisions with 1.0 keV electrons is studied. We observe a series of two- and three-body fragmentation channels which are identified from the correlation map between fragment ions. For all of the channels, the kinetic energy release (KER) distributions are obtained. The Dalitz plot and Newton diagram are adopted to analyze the fragmentation dynamics of the three-body dissociation channels. For C S 2 3 + and C S 2 4 + , both the concerted and sequential fragmentation mechanisms are observed where the concerted mechanism dominates. For C S 2 5 + , only the concerted mechanism is observed. Two types of Coulomb explosion models considering the molecular vibration are adopted to simulate the experimental KER distributions of the three-body channels. While obvious deviations are observed considering each ion during the whole dissociation process with an integer charge, good agreement can be achieved within deviation less than 5% if the charge state of the ions are adopted from ab initio calculations.

The fragmentation dynamics of OCS q+ (q = 2, 3, 4) induced by electron collision at an impact energy of 500 eV is studied. By using the momentum imaging technique, the three dimensional momentum vectors of all the fragments are obtained, which enables us to analyse both the kinetic energy release and the momentum correlations for a certain fragmentation channel. Up to fifteen dissociation channels are analyzed including six, five, and four channels for two-body, and incomplete and complete three-body Coulomb fragmentations. For three-body dissociation, the fragmentation mechanisms are investigated with the help of Dalitz plot and Newton diagram. It is found that the sequential fragmentation involves in OCS 2+ →O+C + +S + with S + emitted first and in OCS 3+ →O + +C + +S + with O-C and C-S bonds breaking first. The remaining channels, however, always dissociate through a concerted mechanism. The relative intensities of the channels are also presented in this work.

The binding energy spectra of cyclopropane in energy range of 9-19 eV have been measured by the high resolution (e, 2e) spectrometer with 0.5 eV energy resolution. The individual electron momentum distributions for the outer valence orbitals including the two Jahn-Teller splitting components for the highest occupied molecular orbital 3e(') have been obtained. Compared with the results of high level quantum chemistry calculations, the observed different intensities of the experimental momentum profiles for the two Jahn-Teller splitting components have been phenomenologically explained, showing the influences caused by the change in molecular geometry at the instant of ionization from doubly degenerate 3e(') orbital on the electron momentum distributions. In addition, the controversial ordering of the two outer valence orbitals 3a(1)(') and 1a(2)(") has also been assigned unambiguously.

Electron momentum distributions for outer valence orbitals of CF2Cl2 have been obtained by (e,2e) electron momentum spectroscopy at an incident energy of 1200 eV + binding energy. The experimental electron momentum profiles are compared with Hartree-Fock and density functional theory (DFT) calculations using B3LYP hybrid functional with the 6-31G and 6-311+G* basis sets. Generally, the shapes of the experimental momentum profiles are well reproduced by DFT calculations using larger basis sets 6-311 + G*. An attempt has been made to clarify the ordering of the outer valence orbitals, which have been in controversy, by comparing experimental results with B3LYP/6-311 + G* calculations., (Copyright 2004 American Institute of Physics)