Laser spectroscopy of radioactive molecules for future searches of new physics

The systematic study of the properties of atomic nuclei with extreme numbers of protons and neutrons has been the focus of nuclear physics for decades. In typical low-energy nuclear physics experiments, the relevant nuclear structure observables are extracted with high precision from the measured energy levels of the atomic system. Recently, the laser-spectroscopic study of radioactive molecules, instead of atoms, that contain the nucleus of interest has emerged as a complex yet very powerful pathway for the study of short-lived nuclei. The additional degrees of freedom that the motion of molecules involves compared to that of an atom promises an improvement of up to three orders of magnitude in the precision of nuclear charge radius measurements. Additionally, extracting the nucleus of interest as part of a molecule is expected to increase the extraction yield from the ISOL target by a few orders of magnitude in multiple cases, thus promising an improvement in the range of nuclei that can be studied. In the course of this doctoral project, the potential of molecular laser spectroscopy for nuclear physics will be explored for the case of short-lived radioactive actinium monofluoride (AcF) isotopologues produced at the ISOLDE facility at CERN and studied with collinear resonant ionization spectroscopy. Actinium is of high interest both for the study of nuclear structure and for the potential of Ac-225 as a medical isotope. The molecular structure of AcF has never been studied with laser spectroscopy before, and shall thus also benchmark the accuracy of state-of-the-art quantum chemistry methods for heavy molecules without stable isotopologues. In addition to the laser spectroscopy of AcF, this doctoral project will contribute to the development of infrastructure for the production and study of radioactive molecules at ISOLDE, as well as the development of specialized ion optics equipment for molecular beams, in an effort towards bridging the gap between ultra-high-precision molecular studies at non-radioactive laboratories and ISOL facilities like CERN-ISOLDE.