Meltzer, Thomas;
(2020)
The calculation of electron collisions with atoms and molecules.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
In this thesis electron collisions are studied under two different scattering energy regimes. Firstly, low energy electron-molecule collisions are considered. These typically occur in interstellar medium, planetary atmospheres or industrial plasmas. Under these conditions the electrons cannot be treated classically and so a quantum mechanical approach is used. Using R-matrix theory two targets are studied: nitric oxide (NO) and molecular hydrogen (H$_2$). Owing to new developments in the UKRMol+ code the boundaries of previous R-matrix calculations are pushed to new limits in order to produce accurate cross-sections for electron-impact electronic excitation of H$_2$. This includes the use of a B-spline continuum basis, a triply-augmented target basis and a box size of 100 $a_0$. NO is used as a prototypical example of an open-shell molecule that exhibits mixed Rydberg-like and Valence states. Systems like this are typically difficult to solve using standard quantum chemistry approaches, and so the R-matrix with pseudo-states method is employed to produce a set of improved potential energy curves, capable of being used in further scattering calculations. In the second regime, high energy electron-atom collisions are investigated. These types of collision take place in strongly-driven systems, e.g., atoms in intense laser fields. In this case, the \emph{scattering} electron is provided by the neutral parent atom as it is ionised by the external field. The specific focus of this work is the phenomena of non-sequential double ionisation. A semiclassical Monte-Carlo method is used based on the three step model, which fully accounts for two active electrons, the Coulomb potential and the magnetic-field. Using this model the role of magnetic-field effects in strong-field physics are investigated.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | The calculation of electron collisions with atoms and molecules |
| Event: | UCL |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2020. Original content in this thesis is licensed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) Licence (https://creativecommons.org/licenses/by/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| Keywords: | Electron Collisions, Strong Field Physics, R-matrix Theory, Semiclassical Monte-Carlo Trajectories |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10108920 |
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