Comment on the accuracy of absolute electron-impact ionization cross sections for molecules

Stebbings, R. F.; Lindsay, B. G.

doi:10.1063/1.1346641

Cited by 26 publications

(11 citation statements)

References 9 publications

(6 reference statements)

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“… Straub et al [1996] directly measured the absolute partial cross sections by extracting, mass analyzing and counting ions formed along a known path length. Stebbings and Lindsay [2001] found that the sum of their partial cross sections to be fully consistent with the total charge production cross section of Rapp and Englander‐Golden [1965]. The error in their data, according to Lindsay and Mangan [2003], is less than ± 5%.…”

Section: Analysis and Resultsmentioning

confidence: 78%

Evaluation of electron impact excitation of N₂ X ¹Σ_g⁺(0) into the N₂⁺ X ²Σ_g⁺(v), A ²Π_u(v), and B ²Σ_u⁺(v) states

Shemansky

Liu

2005

J. Geophys. Res.

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Published experimental integrated electric dipole photoionization oscillator strengths (fij) have been applied to the determination of absolute electron impact excitation cross sections of the N2 X 1Σg+(0) state into the N2+ X 2Σg+(v), A 2Πu(v), and B 2Σu+(v) states. The required relative electron impact cross section shape functions from threshold to energy values, limited by the imposition of relativistic effects at the high end, are established in this work by extracting accurate analytic functions from a critical review of extensive published experimental results. The cross sections examined here are important benchmarks used in establishing absolute values for critical rate processes in aeronomy. The determination of the absolute cross sections using the derived fij is accomplished through the physical relationship to a modified Born approximation analytic function that defines the electron impact shape functions. The zero order term of the analytic function is established in value relative to the remaining terms through shape analysis of the experimental electron impact results. The value of fij fixes the absolute value of the zero order term, determining the cross sections over the entire electron impact energy range. It is argued that this methodology is the most accurate approach at this time because of the existence of the intrinsically more accurate photometrically dermined fij. The critical quantities in atmospheric process applications are the branching ratios of excitation into the N2+ X 2Σg+, A 2Πu, and B 2Σu+ states. The N2+ (X 2Σg+, A 2Πu, B 2Σu+) partitioning within the total ionization cross section has been a source of disagreement in the literature, in spite of the fact that substantial effort has been expended in establishing acceptably accurate values. The present work establishes accurate cross sections for these states over the entire practical energy range required for research in atmospheric N2 physical chemistry. The accuracy of the results obtained here are verified by consistency with the most reliably established past experimental electron impact cross sections, in agreement with the independently established total N2+ cross section. We provide analytic collision strengths for the vibrational levels of the N2+ X 2Σg+, A 2Πu, and B 2Σu+ states, allowing establishment of rate coefficients for the system, at an estimated error ≤±8%.

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Section: Analysis and Resultsmentioning

confidence: 78%

Evaluation of electron impact excitation of N₂ X ¹Σ_g⁺(0) into the N₂⁺ X ²Σ_g⁺(v), A ²Π_u(v), and B ²Σ_u⁺(v) states

Shemansky

Liu

2005

J. Geophys. Res.

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“…The complete collection of ions was achieved. Stebbings and Lindsay [2001] found that the sum of their partial cross sections to be fully consistent with the total charge production cross section of Rapp and Englander‐Golden [1965]. The error in their data, according to Lindsay and Mangan [2003], is less than ±5%.…”

Section: Analysis and Resultsmentioning

confidence: 79%

Analysis of electron impact ionization properties of methane

Liu

Shemansky

2006

J. Geophys. Res.

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“…3,12 It should be noted that the measurements of Vallance et al, 2 Torres et al, 10 and Rapp and Englander-Golden 11 are for total charge production while the present data represent total ion production. 9,14 The congruence of the results of these two independent laboratories is viewed as compelling evidence for the correctness of their collective data. Vallance et al 2 estimated a maximum experimental uncertainty of 4% for their data, but they to be in complete agreement with the present data over the entire energy range.…”

Section: Resultsmentioning

confidence: 89%

Electron-impact ionization of the methyl halides

Rejoub

Lindsay

Stebbings

2002

The Journal of Chemical Physics

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Evaluation of the computational methods for electron-impact total ionization cross sections: Fluoromethanes as benchmarks Absolute partial cross sections for electron-impact ionization of CH4 from threshold to 1000 eV Absolute partial and total cross sections for electron-impact ionization of CH 3 F, CH 3 Cl, CH 3 Br, and CH 3 I are reported for electron energies from threshold to 1000 eV. The product ions are mass analyzed using a time-of-flight mass spectrometer and detected with a position-sensitive detector whose output demonstrates that all product ion species are collected with equal efficiency irrespective of their initial kinetic energies. Data are presented for the production of CH n F ϩ , CH n Cl ϩ , CH n Br ϩ , CH n I ϩ , CH n ϩ , F ϩ , Cl ϩ , Br ϩ , I ϩ , and H ϩ , where nϭ0 -3. Data are also reported for production of H 2 ϩ , H 3 ϩ , and doubly charged species at 100 eV. The total cross section for each target is obtained as the sum of the partial cross sections. The overall uncertainty in the absolute cross sections for most of the singly charged ions is Ϯ6%. It is observed that, although the Deutsch-Märk and the binary-encounter-Bethe theoretical formalisms are able to predict some features of the measured total cross sections, neither is consistently accurate. The simple ab initio method of Vallance et al. can apparently predict the value of the cross section maxima as well as the other more sophisticated approaches.

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Comment on the accuracy of absolute electron-impact ionization cross sections for molecules

Abstract: Absolute partial cross sections for electron-impact ionization of CO 2 from threshold to 1000 eV The Journal of Chemical Physics 105, 4015 (1996) Absolute partial cross sections for electron-impact ionization of and from threshold to 1000 eV

Cited by 26 publications

References 9 publications

Evaluation of electron impact excitation of N₂ X ¹Σ_g⁺(0) into the N₂⁺ X ²Σ_g⁺(v), A ²Π_u(v), and B ²Σ_u⁺(v) states

Evaluation of electron impact excitation of N₂ X ¹Σ_g⁺(0) into the N₂⁺ X ²Σ_g⁺(v), A ²Π_u(v), and B ²Σ_u⁺(v) states

Analysis of electron impact ionization properties of methane

Electron-impact ionization of the methyl halides

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Comment on the accuracy of absolute electron-impact ionization cross sections for molecules

Abstract: Absolute partial cross sections for electron-impact ionization of CO 2 from threshold to 1000 eV The Journal of Chemical Physics 105, 4015 (1996) Absolute partial cross sections for electron-impact ionization of and from threshold to 1000 eV

Cited by 26 publications

References 9 publications

Evaluation of electron impact excitation of N2 X 1Σg+(0) into the N2+ X 2Σg+(v), A 2Πu(v), and B 2Σu+(v) states

Evaluation of electron impact excitation of N2 X 1Σg+(0) into the N2+ X 2Σg+(v), A 2Πu(v), and B 2Σu+(v) states

Analysis of electron impact ionization properties of methane

Electron-impact ionization of the methyl halides

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Product

Resources

About

Evaluation of electron impact excitation of N₂ X ¹Σ_g⁺(0) into the N₂⁺ X ²Σ_g⁺(v), A ²Π_u(v), and B ²Σ_u⁺(v) states

Evaluation of electron impact excitation of N₂ X ¹Σ_g⁺(0) into the N₂⁺ X ²Σ_g⁺(v), A ²Π_u(v), and B ²Σ_u⁺(v) states