Theoretical Studies of Atomic Structure, Radiative Transitions and Interference Effects

Sammanfattning: Theoretical calculations concerning the advanced understanding of atomic structure and transitions has been performed for some atomic systems. The importance of different types of correlation depending on system has been investigated both using relativistic and non-relativistic quantum mechanics. Methods for simplifying the analysis of special types of spectra is presented and transition rates and lifetimes for a wide range of different ions and systems are given. Programs treating ions with or without hyperfine structure in an external magnetic field has been developed. A first test of the accuracy of these has been undertaken, and they have been used in the field free limit to explain the spectra of some hyperfine transitions in Gallium which earlier has not been understood. New ideas concerning interference between different types of multipole transition channels are presented. It is shown that this interference gives rice to M dependent lifetimes of the magnetic sublevels belonging to the same fine or hyperfine structure level. Some of these interference effects has been known, but to our knowledge this is the first time that the idea of hyperfine and Zeeman induced interference effects are put forward. The theory of hyperfine induced interference between a magnetic octupole and an electric quadrupole transition channel has been used to perform calculations of the lifetime of the first excited level in nickel-like xenon. From our results, an experimental lifetime decay curve which earlier has not been understood, could be reproduced and explained.