Computational Atomic Structure: Applications to Astrophysics and Nuclear Structure

Abstract: This thesis deals with the modelling of atoms and ions. In heavy systems, where the effect of the nuclear size must be considered, a fully relativistic treatment based on the Dirac-Coulomb Hamiltonian is needed. Chapter two of the thesis provides an introduction to the basic principles of the fully relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method, which is a variational approach for determining the wave functions. After we demonstrate how to obtain the best approximation of the wave functions by optimizing the energy expression, we describe how to compute the eigenvalues of operators other than the Hamiltonian, and how these eigenvalues correspond to measurable quantities. Chapter three and four, respectively, summarize the work done in the two published papers, illustrating some of the applications of the relativistic atomic structure theory.Paper I is an example of atomic structure calculations for astrophysical applications. Extensive amount of atomic transition data are produced for the systems of neutral and singly ionized aluminium that can be used to improve the interpretation of abundances in stars. Paper II demonstrates a novel method, in which the atomic structure calculations of isotope shifts are combined with experimental data, for extracting nuclear properties other than the charge radii.