Measurements of High-Precision Atomic Data with Applications to Astrophysics and Cosmology

Abstract: Investigations of astrophysical spectra require accurate atomic data, such as wavelengths and transition probabilities. This thesis provides high-precision atomic data for astrophysical and cosmological applications. The measurements have been carried out using Fourier transform spectrometry on light produced in a hollow cathode light source. The variability of fundamental constants is investigated by observations of line-shifts in high-redshift quasar absorption spectra. For this purpose precision wavelengths have been measured for ultraviolet resonance lines visible in such spectra. Accurate laboratory wavelengths have also been determined for parity-forbidden infrared lines visible in spectra from low density astrophysical plasmas, by improving the energy level values. Ritz wavelengths have then been derived from these. The stellar abundances in metal-poor stars are important parameters in the investigations of galaxy evolution. In order to make reliable measurements of the relative elemental abundances in stars, it is necessary to have accurate values for the oscillator strengths of the observable transitions. For this purpose absolute transition probabilities have been measured for prominent Mg I and Ca I lines, by combining radiative lifetimes with branching fractions.