Speaker
Description
To explain the significant baryon asymmetry observed in the universe, a larger source of charge and parity (CP) violation is required [1]. Signatures of such CP-odd properties could be observed as small shifts in the transition frequencies of atoms and molecules [2,3]. Particularly, molecules have become the current most sensitive approach for CP-violation studies due to their strong internal electric field [4]. Furthermore, nuclear CP-violating sources are enhanced in heavy radioactive nuclei with static octupole deformation [5]. Among them, the long-lived 225,227Ac isotopes are expected to be extremely sensitive to nuclear CP-violating moments [6].
In this contribution, we present the first spectroscopy of AcF using the Collinear Resonance Ionization Spectroscopy (CRIS) experiment [7] at ISOLDE. Thanks to its high volatility, the measured 227AcF extraction rates of 6×10^7 ions per second [8] are compatible with current high-precision CP-violation experiments [9]. The excitation energy of the strongest electronic transition from the X1Σ+ ground state, critical for future beyond the SM experiments, was measured and an upper limit on its radiative lifetime was estimated [10]. Our state-of-the-art relativistic coupled cluster and nuclear density functional calculations reveal that AcF is particularly sensitive to measurements of different nuclear CP-odd sources. Due to this enhanced sensitivity, AcF has the potential to constrain the global CP-violation parameter landscape by three orders of magnitude compared to the current limits using a conservative precision setup and lower precision than previously demonstrated in homoelectronic systems [10,11].
[1] Sakharov, A. D. (1998). Violation of CP-invariance, C-asymmetry, and baryon asymmetry of the Universe. In In The Intermissions… Collected Works on Research into the Essentials of Theoretical Physics in Russian Federal Nuclear Center, Arzamas-16 (pp. 84-87).
[2] Safronova, M. S., Budker, D., DeMille, D., Kimball, D. F. J., Derevianko, A., & Clark, C. W. (2018). Search for new physics with atoms and molecules. Reviews of Modern Physics, 90(2), 025008.
[3] Gaul, K., & Berger, R. (2024). Global analysis of CP-violation in atoms, molecules and role of medium-heavy systems. Journal of High Energy Physics, 2024(8), 1-42.
[4] Roussy, T. S., Caldwell, L., Wright, T., Cairncross, W. B., Shagam, Y., Ng, K. B., ... & Cornell, E. A. (2023). An improved bound on the electron’s electric dipole moment. Science, 381(6653), 46-50.
[5] Auerbach, N., Flambaum, V. V., & Spevak, V. (1996). Collective T-and P-odd electromagnetic moments in nuclei with octupole deformations. Physical review letters, 76(23), 4316.
[6] Flambaum, V. V., and V. A. Dzuba. "Electric dipole moments of atoms and molecules produced by enhanced nuclear Schiff moments." Physical Review A 101.4 (2020): 042504.
[7] Cocolios, T. E., De Groote, R. P., Billowes, J., Bissell, M. L., Budinčević, I., Goodacre, T. D., ... & Yang, X. (2016). High-resolution laser spectroscopy with the Collinear Resonance Ionisation Spectroscopy (CRIS) experiment at CERN-ISOLDE. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 376, 284-287.
[8] Au, M., Nies, L., Stegemann, S., Athanasakis-Kaklamanakis, M., Cocolios, T. E., Fischer, P., ... & Rothe, S. (2025). Production and purification of molecular 225Ac at CERN-ISOLDE. Journal of Radioanalytical and Nuclear Chemistry, 334(1), 367-379.
[9] Alauze, X., Lim, J., Trigatzis, M. A., Swarbrick, S., Collings, F. J., Fitch, N. J., ... & Tarbutt, M. R. (2021). An ultracold molecular beam for testing fundamental physics. Quantum Science and Technology, 6(4), 044005.
[10] Athanasakis-Kaklamanakis, M., Au, M., Kyuberis, A., Zülch, C., Gaul, K., Wibowo, H., ... & Yang, X. F. (2025). Laser spectroscopy and CP-violation sensitivity of actinium monofluoride. arXiv preprint arXiv:2507.05224, under review at Nature, July 2025
[11] Cho, D., Sangster, K., & Hinds, E. A. (1989). Tenfold improvement of limits on T violation in thallium fluoride. Physical review letters, 63(23), 2559.
