| Popis: |
In this thesis, we are looking for physics beyond the standard model using atomic and molecular measurements. In particular, isotope shifts in atomic spectra can be used to search for new particles. A King plot is a tool that is traditionally used to extract changes in nuclear properties between isotopes, and a simple linear relation between isotope shifts in different spectral lines is often assumed. However, it is expected that this linear relation will break under the influence of new particles that couple electrons and neutrons. As the precision of isotope shift measurements improve, these new particles may be indirectly probed using King Plots. Non-linearities in the King plot can also arise from Standard Model sources, which may obscure new particle signals. Once known, we can factor them out to create a King plot that is only non-linear in the presence of new particles. In this thesis I characterise and estimate the size of dominant standard model non-linearity contributions in several good candidates for isotope shift experiments. The search for new physics also requires precise, ab-initio atomic structure calculations in order to place bounds on new particles and interpret isotope shift experiments. In this thesis, I test the convergence of novel numerical methods for calculating atomic spectra to a high level of accuracy. I present calculations of electronic energy levels and isotope shifts in Tantalum and it’s superheavy analogue Dubnium. I then characterise the closed-shell atom Neon using these new methods and compare the spectral lines and isotope shifts with new experimental data. I also calculate new particle contributions to the isotope shift in neutral and singly-ionised Ytterbium and infer the sensitivity of the resulting King plot to new physics in order to support ongoing experiments. Finally, parity violation experiments aim to test weak nuclear force theory. Current disagreements between measurements suggest the potential for new physics. The interaction between nucleons and electrons via the Anapole Moment leads to parity violating effects that are enhanced in molecules. I have calculated the observable effects of parity violation in Mercury Hydride and determined it to be an ideal molecule for future experiments. |
