On the Quantitative Determination of Cross Sections of Ionization of Molecules by Electronic Collisions

Deutsch, Hans‐Peter; Schmidt, Martin

doi:10.1002/ctpp.19840240504

Cited by 18 publications

(5 citation statements)

References 30 publications

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“…The DM approach also works well for hydrocarbons. 35 The BEB cross sections for CH 2 and CH 3 are compared to the experimental data by Baiocchi et al 36 for CD 2 ͑Fig. 9͒ and CD 3 ͑Fig.…”

Section: Hydrocarbonsmentioning

confidence: 99%

New model for electron-impact ionization cross sections of molecules

Hwang¹,

Kim

Rudd³

1996

The Journal of Chemical Physics

529

362

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A theoretical model for electron-impact ionization cross sections, which has been developed primarily for atoms and atomic ions, is applied to neutral molecules. The new model combines the binary-encounter theory and the Bethe theory for electron-impact ionization, and uses minimal theoretical data for the ground state of the target molecule, which are readily available from public-domain molecular structure codes such as GAMESS. The theory is called the binaryencounter Bethe (BEB) model, and does not, in principle, involve any adjustable parameters. Applications to 19 molecules, including H 2 , NO, CH 2 , C 6 H 6 , and SF 6 , are presented, demonstrating that the BEB model provides total ionization cross sections by electron impact from threshold to several keV with an average accuracy of 15% or better at the cross section peak, except for SiF 3 . The BEB model can be applied to stable molecules as well as to transient radicals. History:Received 13 A theoretical model for electron-impact ionization cross sections, which has been developed primarily for atoms and atomic ions, is applied to neutral molecules. The new model combines the binary-encounter theory and the Bethe theory for electron-impact ionization, and uses minimal theoretical data for the ground state of the target molecule, which are readily available from public-domain molecular structure codes such as GAMESS. The theory is called the binary-encounter Bethe ͑BEB͒ model, and does not, in principle, involve any adjustable parameters. Applications to 19 molecules, including H 2 , NO, CH 2 , C 6 H 6 , and SF 6 , are presented, demonstrating that the BEB model provides total ionization cross sections by electron impact from threshold to several keV with an average accuracy of 15% or better at the cross section peak, except for SiF 3 . The BEB model can be applied to stable molecules as well as to transient radicals.

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Section: Hydrocarbonsmentioning

confidence: 99%

New model for electron-impact ionization cross sections of molecules

Hwang¹,

Kim

Rudd³

1996

The Journal of Chemical Physics

529

362

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“…The conventional additivity rule as introduced by O ¨tvos and Stevenson 6 and refined by Fitch and Sauter 7 and Deutsch and Schmidt 8 uses the concept that the molecular ionization cross section σ can be expressed in the form where b is a constant, n i is the number of atoms "i" in the molecule, and σ i is the constant contribution of each atom "i" to the molecular ionization cross section. The additivity concept as represented by eq 1 is in principle not capable of reproducing the "inversion" of the molecular ionization cross sections which was first observed experimentally for the SiF x (x ) 1-3) free radicals [19][20][21] and discussed by Deutsch et al 22 "Inversion" here refers to the fact that the total single ionization cross section † Ernst-Moritz-Arndt Universita ¨t.…”

Section: Concept Of the Modified Additivity Rulementioning

confidence: 99%

“…in fusion edge plasmas and in plasma processing) has stimulated the use of simplistic additivity rules to estimate molecular ionization cross sections. Many variants of the additivity rule, whose concept was first introduced by Ötvos and Stevenson, can be found in the literature. , They all rely on the concept that the molecular ionization cross section is derived by adding in some fashion the ionization cross sections of the atomic constituents of the molecule with or without accounting for molecular bonding and/or weighting factors for the atomic cross sections. In addition to these rather simple approaches, there have been semiempirical and semiclassical approaches − including the DM formalism, , geometric approaches, , and the more rigorous Binary−Encounter Bethe (BEB) theory of Kim and collaborators − which combines the additivity concept with quantum mechanically calculated molecular quantities.…”

Section: Introductionmentioning

confidence: 99%

Application of the Modified Additivity Rule to the Calculation of Electron-Impact Ionization Cross Sections of Complex Molecules

et al. 1998

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This paper describes the application of the modified additivity rule (MAR) to the calculation of total (counting) electron-impact ionization cross sections of complex molecules with sum formulas of the form A x B y , A x B y C z , and A p B s C t D u . The MAR incorporates weighting factors for the contributions to the molecular ionization cross section from the ionization cross sections of the constituent atoms, which depend explicitly on the atomic radii and the effective number of atomic electrons except for a few special cases (hydrides where the other constituent atom has a radius smaller than the radius of the H atom and species where both constituent atoms have radii smaller than the radius of the H atom), where the weighting factors depend only on the atomic radii, i.e., on geometric effects. A comprehensive comparison of the predictions of the modified additivity rule with available experimental data and with other theoretical predictions is presented.

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“…Relatively less research of electron scattering deals with the CH3F molecule. Investigations of the total ionization cross section were performed by Beran and Kevan (1969) (experimentally) and Deutsch and Schmidt (1984) (semi-empirically). Griffiths and Harris (1988) measured single-and double-ionization energies.…”

Section: Introductionmentioning

confidence: 99%

Electron-methyl halides scattering. Total cross section measurements for methyl chloride and methyl fluoride

Krzysztofowicz

Szmytkowski

1995

J. Phys. B: At. Mol. Opt. Phys.

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Electron uansmission experiments have been carried out in CH3F and CH3Q io the energy range between 0.3 and 250 eV. Absolute values for total cross sections are presented and compared with the available data of other groups. The present cross sections are found to be in good agreement with other experiments for CH3F in the overlapping range of energies but deviate significantly from prior results in the w e of CH3C1. Our present measurements, together with previous ones for CHjBr and CH31, canfirm the correlation between static elecuic dipole polarizability of investigated targets and total cross sections at intermediate energies.

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On the Quantitative Determination of Cross Sections of Ionization of Molecules by Electronic Collisions

Cited by 18 publications

References 30 publications

New model for electron-impact ionization cross sections of molecules

New model for electron-impact ionization cross sections of molecules

Application of the Modified Additivity Rule to the Calculation of Electron-Impact Ionization Cross Sections of Complex Molecules

Electron-methyl halides scattering. Total cross section measurements for methyl chloride and methyl fluoride

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