Development of computational relativistic atomic theory with application to the oxygen spectra in astrophysical systems

© 2016 Truong Vo Bang NguyenOver many decades, atomic spectroscopy has repeatedly proven to be one of the most widely used applications across various different fields as it allows the detection, identification, and quantification of chemical species present within a particular sample. This is particularly true in the studies of astrophysics and cosmology. This thesis includes the development of new codes for the calculation of the electron self-energy – a quantum electrodynamic effect – as part of the relativistic atomic structure package grasp2k . The codes are shown to bring results towards better agreement with experimental as well as some of the most advanced atomic theories to date. Moreover, a review into the Breit interaction was conducted to address claims that the method of implementation can affect the overall results as well as the quality of gauge convergence. The theoretical development was used to study two oxygen forbidden lines that feature prominently in the aurora as observed on Earth, namely the green and ultraviolet lines with nominal wavelengths of 557.7nm and 297.2nm, respectively. Many have researched into these forbidden lines either through observation of the aurora, or experimentally measured in the laboratory, or theoretical calculations, dating back to the 1930s. Despite such tremendous effort spanning many decades, major discrepancies between observation, measurement, and theory remain. We also explore other optically allowed transitions of ionised oxygen, which showed great consistencies in our methodology. Fully relativistic atomic theories are employed for the first time in the calculation of these particular lines, with excellent overall results and convergence