Quantum‐Mechanical Calculations of Cross Sections for Electron Collisions With Atoms and Molecules

Abstract

An overview of quantum‐mechanical methods to generate cross‐section data for electron collisions with atoms and molecules is presented. Particular emphasis is placed on the time‐independent close‐coupling approach, since it is particularly suitable for low‐energy collisions and also allows for systematic improvements as well as uncertainty estimates. The basic ideas are illustrated with examples for electron collisions with argon atoms and methane. For many atomic systems, such as e‐Ar collisions, highly reliable cross sections can now be computed with quantified uncertainties. On the other hand, while electron collision calculations with molecules do provide key input data for plasma models, the methods, and computer codes presently used require further development to make these inputs robust.

e± Ar scattering in the energy range 1 eV ≤ E i ≤ 0.5 GeV

“…Integral, total and ionization cross sections figure 1 presents our OPM results of the integrated elastic σ el , momentum transfer σ m , viscosity σ v , absorption σ abs , total σ tot and total ionization σ ion cross sections for electron impact scattering at 1 eVE i 10 keV in comparison with the available experimental data and other theoretical results. As seen in figure 1(a), the present σ el results are in good agreement both qualitatively and quantitatively with the experimental data [59][60][61] as well as with other theoretical findings [18,43,62] with a slight underestimation below around 2 eV. Figure 1(b) compares our OPM predictions for σ m with the experimental data [59][60][61] and the calculations of [18,63].…”

“…Since the first electron-atom scattering experiments in 1931 [5], many theoretical and experimental studies on e ± -Ar have been available in the literature [6][7][8]. Apart from these investigations, the experimental works of Ranković et al [9], Zecca et al [10], Jones et al [11], Kurokawa et al [12], Cho and Park [13], Hargreaves et al [14], Milosavljević et al [15], Mielewska et al [16] and Gilbert et al [17], and the theoretical calculations of Ranković et al [9], Bartschat et al [18], Green et al [19], Fursa and Bray [20], Jones et al [11], Mohan et al [21], McEachran and Stauffer [22], Bote et al [23], Gargioni and Grosswendt [4], Adibzadeh and Theodosiou [24], Yousif Al-Mulla [25], Jablonski et al [26], Salvat [27], Stepanek [28], Blanco and García [29,30], Paikeday and Alexander [31], Kelemen [32], Bartlett and Stelbovics [33], Sienkiewicz et al [34] and Pandya and Shah [35], are worth mentioning among the important works.…”

The 2017 Plasma Roadmap: Low temperature plasma science and technology

“…Unfortunately, computational studies on electron-molecule collisions, while increasingly supplying data on key processes, cannot yet be performed with complete confidence for many key problems [180], in particular leading to the dissociation of the molecule, for example, by low energy dissociation electron attachment (DEA). More than a dozen international groups are now pursuing VMI studies to quantify the dissociation dynamics of DEA and dipolar dissociation.…”

“…Several advances in methodology have the potential to provide benchmark A+M data for the plasma community. For electron-atom collisions, the development of sophisticated methods based on the use of a very extensive basis set of expansions has led to benchmark results for such processes with a high degree of predictability [180].…”

Special Issue on Numerical Modelling of Low‐Temperature Plasmas for Various Applications – Part I: Review and Tutorial Papers on Numerical Modelling Approaches

“…Collision cross sections can be experimentally measured, but they can also be generated from quantum‐mechanical calculations, e.g., for electron scattering. The latter is explained by Bartschat, Tennyson and Zatsarinny (Drake University and University College London) who present an overview of various quantum‐mechanical methods, with special focus on the time‐independent close‐coupling approach . Examples are shown for electron collisions with both atoms (Ar) and molecules (CH 4 ).…”