Precision spectroscopy of RaF molecules for fundamental physics

Compared to atoms, molecules can offer more than five orders of magnitude enhanced sensitivity to violations of fundamental symmetries, enabling the possibility to probe energy scales beyond hundreds of TeV. Containing octupole-deformed nuclei, radium monofluoride (RaF) is expected to be highly sensitive to the parity-violating nuclear anapole moment as well as to the parity- and time-reversal violating nuclear Schiff and magnetic quadrupole moments. In this talk, I will present the latest results obtained from a series of laser spectroscopy experiments performed on short-lived RaF molecules. I will first describe a measurement of the isotope shift of five RaF isotopologues, ^{223 - 226 , 228}RaF. These results demonstrate the particularly high sensitivity of RaF to nuclear size effects, offering a stringent test of models describing the electronic density within the radium nucleus. I will then show preliminary results from high-resolution laser spectroscopy experiments of ²²³RaF and ²²⁶RaF. Rotational and hyperfine constants of these two isotopologues will be presented. These results represent the first of their kind performed on radioactive, short-lived molecules, opening the way for precision studies and new physics searches in these systems.

This work was supported the ERC Consolidator Grant No. 648381 (FNPMLS); the Office of Nuclear Physics, U.S. Department of Energy, under Grants DESC0021176 and DE-SC0021179; the MISTI Global Seed Funds; Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) - Projektnummer 328961117 - SFB 1319 ELCH; STFC Grants ST/L005794/1, ST/P004423/1 and ST/L005786/1 and Ernest Rutherford Grant No. ST/L002868/1; projects from FWOVlaanderen, GOA 15/010 from KU Leuven and BriX IAP Research Program No. P7/12; the European Unions Grant Agreement 654002 (ENSAR2); the Russian Science Foundation under Grant N 18-12-00227 (year 2020) and 21-42-04411 (year 2021); the BMBF Grants 05P15HGCIA and 05P18HGCIA.