Dirac R-matrix calculations in support of astrophysical and magnetically confined plasma diagnostics

Abstract

In this thesis, relativistic atomic structure calculations and electron-impact excitation calculations are presented for the first three ion stages of gold, the first three ion stages of platinum and doubly ionised tungsten. The atomic data computed for gold and platinum is relevant in astrophysical plasma diagnostics, specifically in the study of neutron star mergers as the origin of the elements heavier than iron. Doubly ionised tungsten has an important application to the investigation of erosion and impurity influx in magnetically confined fusion plasmas.

To accurately calculate the atomic structure data for these species the GRASP0 computer package was used. In addition, to describe the electron-impact excitation the Dirac atomic R-matrix codes (DARC) were employed. To investigate the plasma diagnostics the collisional radiative code ColRadPy was utilised. The underlying theory informing each of these computations is discussed in detail in this thesis along with a description of the codes used.

The results of the atomic structure calculations for each of the species (Au I-III, Pt I-III, W III) will be presented and compared to experimental values for level energies and transition rates, where available. Additionally, the results of the electron-impact excitation calculations using the R-matrix method will be presented. Employing collisional radiative theory these results will be then be used to investigate metastable populations, LTE assumptions and help with line identification in experimental spectra.

Thesis is embargoed until 31 July 2025.

Date of Award	Jul 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Northern Ireland Department for the Economy
Supervisor	Connor Ballance (Supervisor) & Catherine Ramsbottom (Supervisor)