Absolute total electron impact ionization cross-sections for perfluorinated hydrocarbons and small halocarbons

Bart, Mark; Harland, Peter W.; Hudson, James E.; Vallance, Claire

doi:10.1039/b009243f

Cited by 85 publications

(114 citation statements)

References 10 publications

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“…The ion source consists of a four-element arrangement: a repeller shield behind the filament, an extractor and mesh cage, a focusing lens, and an earthed lens attached to the end of the quadrupole. The potentials applied to these elements were tuned experimentally so that the functional form of the energy-dependent total ion production efficiency reproduced that of TICSs measured using an alternative apparatus designed for unit collection efficiency [44,45]. Ion trajectory simulations carried out using the SIMION 8.0.4 [46] software package confirmed that these experimentally optimized potentials allowed collection of the majority of ion fragments that might be produced with high KER.…”

Section: Experimental Methodsmentioning

confidence: 94%

Electron-impact-ionization dynamics of five C2to C4perfluorocarbons

et al. 2013

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Reprinted with permission from the American Physical Society: Phys. Rev. A 88, 062710 c (2013) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Perfluorocarbons (PFCs) are man-made compounds whose ion physics exhibit complex interplays between statistical and nonstatistical fragmentation and intramolecular rearrangement processes. One probe of such processes is the energy-dependent electron-impact-ionization cross section. Partial electron-impact-ionization cross sections are reported for the fragments arising from five C 2 to C 4 PFCs, namely, C 2 F 6 , C 3 F 8 , C 3 F 6 , CF 2 =CF-CF=CF 2 , and CF 3 -C≡C-CF 3 , over the energy range from threshold to ∼210 eV. Care was taken to maximize ion collection efficiency and to minimize discrimination against ions produced with high kinetic-energy release, and the measured cross sections have been calibrated using independent absolute total (gross) ionization efficiency curves measured previously in the same laboratory with an instrument that was designed to essentially have unit detection efficiency. Total ionization cross sections have also been modeled using the binary-encounter Bethe model, and the shortcomings of the model when applied to perfluorinated compounds are discussed. Analysis of the mass spectral fragmentation patterns in combination with ab initio energetics suggests that nonstatistical dissociative ionization processes play a significant role in the fragmentation dynamics of saturated PFCs. In contrast, unsaturated PFCs exhibit long-lived parent ions, which tend to undergo a higher degree of statistical dissociation following ionization, involving considerable intramolecular rearrangement.

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Section: Experimental Methodsmentioning

confidence: 94%

Electron-impact-ionization dynamics of five C2to C4perfluorocarbons

et al. 2013

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“…Note that the data for CF 4 and CCl 4 were reported previously by our group 1,6 and are included here simply for comparison with the present results. For 18,19 Also included in these figures are the available experimental and theoretical total cross sections, [22][23][24][25][55][56][57] elastic ICSs using the SMC approach, 20 and experimental [58][59][60][61][62]64 and BEB theoretical 63 …”

Section: Resultsmentioning

confidence: 99%

“…[22][23][24][55][56][57] In addition, the results from the present IAM-SCAR calculations for the elastic ICS, total cross sections and sum over all inelastic ICS (except vibrational excitations) are also plotted. Note that independent ionization cross sections [58][59][60][61][62][63][64] are also shown for each species, where applicable, to illustrate the efficacy of the BEB model approach. In Figs.…”

Section: Integral and Momentum Cross Sectionsmentioning

confidence: 99%

Cross sections for elastic scattering of electrons by CF3Cl, CF2Cl2, and CFCl3

Hoshino

Horie

Kato

et al. 2013

The Journal of Chemical Physics

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Differential, integral, and momentum transfer cross sections have been determined for the elastic scattering of electrons from the molecules CF3Cl, CF2Cl2, and CFCl3.With the help of a crossed electron beam–molecular beam apparatus using the relative flow technique, the ratios of the elastic differential cross sections (DCSs) of CF3Cl, CF2Cl2, and CFCl3 to those of He were measured in the energy region from 1.5 to 100 eV and at scattering angles in the range 15° to 130°. From those ratios, the absolute DCSs were determined by utilizing the known DCS of He. For CF3Cl and CF2Cl2, at the common energies of measurement, we find generally good agreement with the results from the independent experiments of Mann and Linder [J. Phys. B 25, 1621 (1992)10.1088/0953-4075/25/7/030; Mann and Linder J. Phys. B 25, 1633 (1992)10.1088/0953-4075/25/7/031]. In addition, as a result of progressively substituting a Cl-atom, undulations in the angular distributions have been found to vary in a largely systematic manner in going from CF4 to CF3Cl to CF2Cl2 to CFCl3 and to CCl4. These observed features suggest that the elastic scattering process is, in an independently additive manner, dominated by the atomic-Cl atoms of the molecules. The present independent atom method calculation typically supports the experimental evidence, within the screened additivity rule formulation, for each species and for energies greater than about 10–20 eV. Integral elastic and momentum transfer cross sections were also derived from the measured DCSs, and are compared to the other available theoretical and experimental results. The elastic integral cross sections are also evaluated as a part of their contribution to the total cross section.

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“…Finally, the experimental and theoretical elastic ICSs for 1,3-C 4 F 6 , 2-C 4 F 6 , and c-C 4 F 6 , are plotted in Fig. 4, respectively, along with available experimental and theoretical literature data on the total cross sections, 5 and experimental data on the ionization 17 and attachment cross sections. 18 Note, as mentioned above, that there is no previous theoretical data on the C 4 F 6 isomers available for comparison except from the present calculation.…”

Section: Theoretical Approach (Iam-scar) Fitting and Integratiomentioning

confidence: 99%

“…In addition, the results from the present IAM-SCAR calculations for the elastic ICS, total cross sections, and sum over all inelastic ICSs (except vibrational excitations) are also plotted. Note that independent ionisation cross sections 17 are also shown for each species, where available, to illustrate the efficacy of the BEB model approach.…”

Section: Comparison Of Integral and Total Cross Sectionsmentioning

confidence: 99%

Elastic differential cross sections for C4F6 isomers in the 1.5–200 eV energy electron impact: Similarities with six fluorine containing molecules and evidence of F-atom like scattering

Hoshino

Limão‐Vieira

Anzai

et al. 2014

The Journal of Chemical Physics

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We report absolute elastic differential cross sections for electron interactions with the C 4 F 6 isomers, hexafluoro-1,3-butadiene (1,3-C 4 F 6 ), hexafluoro-2-butyne (2-C 4 F 6 ), and hexafluorocyclobutene (c-C 4 F 6 ). The incident electron energy range is 1.5-200 eV, and the scattered electron angular range for the differential measurements varies from 15 • to 150 • . In all cases the absolute scale of the differential cross section was set using the relative flow technique, with helium as the reference species. Atomic-like behaviour in these scattering systems is shown here for the first time, and is further investigated by comparing the elastic cross sections for the C 4 F 6 isomers with other fluorinated molecules, such as SF 6 and C n F 6 (n = 2, 3, and 6). We note that for all the six-F containing molecules, the scattering process for electron energies above 30 eV is indistinguishable. Finally, we report results for calculations of elastic differential cross sections for electron scattering from each of these isomers, within an optical potential method and assuming a screened corrected independent atom representation. The level of agreement between these calculations and our measurements is found to be quite remarkable in all cases.

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Absolute total electron impact ionization cross-sections for perfluorinated hydrocarbons and small halocarbons

Cited by 85 publications

References 10 publications

Electron-impact-ionization dynamics of five C2to C4perfluorocarbons

Electron-impact-ionization dynamics of five C2to C4perfluorocarbons

Cross sections for elastic scattering of electrons by CF3Cl, CF2Cl2, and CFCl3

Elastic differential cross sections for C4F6 isomers in the 1.5–200 eV energy electron impact: Similarities with six fluorine containing molecules and evidence of F-atom like scattering

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