Laser spectroscopy and CP-violation sensitivity of actinium monofluoride
The apparent invariance of the strong nuclear force under combined charge conjugation and parity (CP) remains an open question in modern physics<sup>1,2</sup>. Precision experiments with heavy atoms and molecules can provide stringent constraints on CP violation via searches for effects due to permanent electric dipole moments and other CP-odd properties in leptons, hadrons and nuclei<sup>3</sup>. Radioactive molecules have been proposed as highly sensitive probes for such searches<sup>4</sup>, but experiments with most such molecules have so far been beyond technical reach. Here we report the production and spectroscopic study of a gas-phase actinium molecule, <sup>227</sup>AcF. We observe the predicted strongest electronic transition from the ground state, which is necessary for efficient readout in searches of symmetry-violating interactions. Furthermore, we perform electronic- and nuclear-structure calculations for <sup>227</sup>AcF to determine its sensitivity to various CP-violating parameters, and find that a realistic, near-term experiment with a precision of 1 mHz would improve current constraints on the CP-violating parameter hyperspace by 3 orders of magnitude. Our results thus highlight the potential of <sup>227</sup>AcF for exceptionally sensitive searches of CP violation.
Authors
- J. Ballof (ORCID: https://orcid.org/0000-0003-0874-500X)
- C. M. Fajardo-Zambrano (ORCID: https://orcid.org/0000-0002-6088-6726)
- J. R. Reilly
- Carsten Zülch (ORCID: https://orcid.org/0009-0007-2563-1342)
- Á. Koszorús (ORCID: https://orcid.org/0000-0001-7959-8786)
- J. Dobaczewski (ORCID: https://orcid.org/0000-0002-4158-3770)
- Alexander A. Breier (ORCID: https://orcid.org/0000-0003-1086-9095)
- K. T. Flanagan (ORCID: https://orcid.org/0000-0003-0847-2662)
- T. E. Cocolios (ORCID: https://orcid.org/0000-0002-0456-7878)
- K. M. Lynch (ORCID: https://orcid.org/0000-0001-8591-2700)
- R. Berger
- S. Kujanpää (ORCID: https://orcid.org/0000-0002-5709-3442)
- Anastasia Borschevsky (ORCID: https://orcid.org/0000-0002-6558-1921)
- G. Neyens (ORCID: https://orcid.org/0000-0001-8613-1455)
- S. Rothe (ORCID: https://orcid.org/0000-0001-5727-7754)
- J. D. Johnson (ORCID: https://orcid.org/0000-0003-4397-5732)
- M. Au (ORCID: https://orcid.org/0000-0002-8358-7235)
- R. P. de Groote (ORCID: https://orcid.org/0000-0003-4942-1220)
- L. Nies (ORCID: https://orcid.org/0000-0003-2448-3775)
- L. V. Skripnikov (ORCID: https://orcid.org/0000-0002-2062-684X)
- L. Lalanne (ORCID: https://orcid.org/0000-0003-1207-9038)
- N. S. Mosyagin (ORCID: https://orcid.org/0000-0002-9158-494X)
- Aleksandra A. Kyuberis (ORCID: https://orcid.org/0000-0001-7544-3576)
- D. Hanstorp (ORCID: https://orcid.org/0000-0001-6490-6897)
- Abigail McGlone (ORCID: https://orcid.org/0000-0003-4424-865X)
- Miranda Nichols (ORCID: https://orcid.org/0000-0003-3693-7295)
- B. van den Borne (ORCID: https://orcid.org/0000-0003-3348-7276)
- Y. C. Liu
- S. Bara (ORCID: https://orcid.org/0000-0001-7129-3486)
- Herlik Wibowo (ORCID: https://orcid.org/0000-0003-4093-0600)
- X. F. Yang
- Konstantin Gaul (ORCID: https://orcid.org/0000-0002-6990-6949)
- Anaïs Dorne (ORCID: https://orcid.org/0000-0002-4014-5816)
- M. Athanasakis-Kaklamanakis (ORCID: https://orcid.org/0000-0003-0336-5980)
- Cyril Bernerd (ORCID: https://orcid.org/0000-0002-2183-9695)
- R. F. García Ruíz (ORCID: https://orcid.org/0000-0002-2926-5569)
- J. Wessolek (ORCID: https://orcid.org/0000-0001-9804-5538)
- K. Chrysalidis (ORCID: https://orcid.org/0000-0003-2908-8424)
- Wouter Ryssens (ORCID: https://orcid.org/0000-0002-4775-4403)
- Fabian C. Pastrana Cruz (ORCID: https://orcid.org/0009-0008-7469-7513)
- S. G. Wilkins (ORCID: https://orcid.org/0000-0001-8897-7227)
- S. Franchoo
Institutions
- University of Kassel (DE)
- Université Libre de Bruxelles (BE)
- Philipps University of Marburg (DE)
- University of Groningen (NL)
- GSI Helmholtz Centre for Heavy Ion Research (DE)
- Johannes Gutenberg University Mainz (DE)
- Peking University (CN)
- Université Paris-Saclay (FR)
- University of Manchester (GB)
- Helmholtz Institute Mainz (DE)
- Laboratoire de Physique des 2 Infinis Irène Joliot-Curie (FR)
- Infection et inflammation (FR)
- State Key Laboratory of Nuclear Physics and Technology
- Technische Universität Berlin (DE)
- Imperial College London (GB)
- University of York (GB)
- Massachusetts Institute of Technology (US)
- European Organization for Nuclear Research (CH)
- University of Gothenburg (SE)
- University of Jyväskylä (FI)
- KU Leuven (BE)
Publication Details
- Journal
- Nature
- Published
- 2025-12-17
- DOI
- https://doi.org/10.1038/s41586-025-09814-1
- Primary Topic
- Nuclear physics research studies
- Type
- article
- Field-Weighted Citation Impact
- 0.00
Funders
- U.S. Department of Energy
- CERN
- Leverhulme Trust
- European Commission
- Deutsche Forschungsgemeinschaft
- Rijksuniversiteit Groningen
- Bundesministerium für Bildung und Forschung
- Fonds Wetenschappelijk Onderzoek
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek
- KU Leuven
- Vetenskapsrådet
- HORIZON EUROPE Framework Programme
- Science and Technology Facilities Council
- Nuclear Physics