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Title: The calculation of electron collisions with atoms and molecules
Author: Meltzer, Thomas
ISNI:       0000 0004 9359 5743
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2020
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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 (H₂). 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 H₂. This includes the use of a B-spline continuum basis, a triply-augmented target basis and a box size of 100 a₀. 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 '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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available