Title:
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Single and double ionisation processes within an intermediate energy R-Matrix framework
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This thesis makes use of the intermediate energy R-matrix approach (IERM) in computationally
modelling various single and double ionisation processes. The basis used in the IERM
approach is an ideal candidate for representing a double electron continua in a time-dependent
or time-independent, general N-electron R-matrix code and one of the main objectives of the
thesis is to explore the efficacy of the basis used in the IERM approach in representing a
double-electron continua. To do this, the IERM method is applied to the study of photoionisation
and photo-double-ionisation of various He-like and Be-like atoms and ions in the
ground and excited initial states, and preliminary calculations of electron impact excitation
involving high lying energy levels of H is investigated with the two-dimensional R-matrix
propagator package. The convergence of the basis for these processes is examined. Throughout
the thesis the results obtained with the IERM method are compared to experimental
results and those from other state of the art theoretical approaches, and agreement is excellent
in all cases. In the case of He-like and Be-like atoms and ions, trends in moving along
the isoelectronic sequences and between the ground and various excited states are analysed
and compare well with existing models where available. The data presented is also of use in
astrophysical applications, to experimentalist and to other theorist who wish to study these
or similar systems. The IERM basis is shown to be capable of representing a double electron
continua and directions in which further work in this field could take are highlighted.
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