Precision studies of radioactive molecules relevant to fundamental physics*

Certain molecules that contain heavy, deformed radioactive nuclei are predicted to be exceptionally sensitive laboratories to examine the fundamental symmetries of nature [1-4]. Despite their recognized potential, technical challenges prevented experimental studies of these systems until very recently. The first landmark study of a short-lived molecule was able to determine the rovibronic structure of different isotpologues of radium monofluoride [5,6] , a promising system in which to search for signatures of symmetry violations.

This contribution presents results from subsequent experimental campaigns in which a massive improvement in resolution enabled an unprecedented glimpse into the structure of the radioactive ^223,225,226RaF. This allowed the laser cooling scheme of ²²⁶RaF to be established which will be critical for realizing future high-precision studies. Furthermore, the hyperfine structure in ²²⁵RaF is shown to be highly sensitive to the Bohr-Weisskopf effect, laying the foundation for the first studies of the distribution of nuclear magnetization in a molecule. Additional results characterising a plethora of newly observed excited electronic states as well as an accurate determination of the molecule's ionization potential will also be presented.

[1] Altuntaş, E. et al., Phys. Rev. Lett. 120, 142501 (2018)

[2] ACME Collaboration, Nature 562, 355–360 (2018)

[3] Flambaum, V. V. et al., Phys. Rev. Lett. 113, 103003 (2014)

[4] Berger, R. et al., WIREs Comput. Mol. Sci. 9, e1396 (2019)

[5] Garcia Ruiz, R. F. et al., Nature 581 396–400 (2020)

[6] Udrescu, S. M. et al. Phys. Rev. Lett. 127 03301 (2021)