Electron-impact multiple ionization of Ne, Ar, Kr and Xe

Abstract

This work describes the multiple ionization cross sections of rare gases by electron-impact. We pay special attention to the high energy region (0.1-10 keV) where the direct ionization is a minor contribution and the post-collisional electron emission dominates the final target charge state. We report here electron-impact single to sextuple ionization cross sections and total ionization cross sections including direct and post-collisional processes, even in the total values. We use the continuum distorted wave and the first Born approximations adapted to describe light-particle impact, i.e. energy, mass and trajectory corrections are incorporated, the latter by considering the electron-target potential and by using the Abel transformation. Auger-type post-collisional contributions are included in the multinomial expansion through experimental branching ratios after single ionization events. Tabulations of these experimental branching ratios for all the orbitals of the four targets are included. Present results are compared with the large amount of electron-impact experimental data available. We have obtained a good description of the multiple-ionization measurements at high energies, where the post-collisional ionization dominates. At intermediate energies, our theoretical results show the correct tendency, with the electron-impact ionization cross sections being far below the proton-impact ones.

On the use of additivity rules to estimate electron production cross sections in proton-biomolecule collisions

“…In this respect, the ARs (6), (7) overestimate the total cross section for H + + NH 3 , because they are based on data for collisions with N 2 , and the electrons are released more easily from the π orbitals of N 2 than from the N-H σ bonds of NH 3 . There is a general good agreement betwen our results and the CDW-EIS calculations of references [19,21] and [23] for energies above that of the maximum of the corresponding TCS, while these calculations underestimate the cross sections at low energies, as can be observed by comparison with the experimental data and the CTMC calculation [20] for H + + H 2 O collisions. As a conclusion of these comparisons, the additivity rules (2) -(9) are useful to estimate total cross sections for electron production in proton collisions with small molecules in a wide energy range, 10 ≤ E ≤ 1000 keV.…”

“…The "humps" in the experimental curves might arise from interference effects between collisions with different atoms, not included in the ARs and that cannot be described by the calculations of references [5] and [10], where the SDCS are obtained by adding the cross sections for EP from all the atomic orbitals weighted by the electron populations on each target molecular orbital (see also the comment of reference [21] on this point).…”

Calculation of Stark resonance parameters for valence orbitals of the water molecule

“…The direct application of these orbitals for collisional or strong-field studies does represent significant computational and methodological challenges. An application of the SCF method using a single-center Slater basis has been available [19][20][21], and has been used in some collision studies [22]. The molecular orbitals for water from [21] have been compared to experimental electron spectroscopy studies [23], and also to more sophisticated calculations, and were found to give reasonable agreement with observations.…”

Theoretical study of the Electron energy distribution Function and the ionization coefficient for pure Krypton, Chlorine discharge and their mixtures

“…The choice of Krypton as a host medium gas for interactions with the atoms and molecules of guest gases (as chlorine) depend on the availability of their energy cross-sections for elastic and inelastic type's interactions [7].…”