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Te use of radioactive molecules for fundamental physics research is a developing interdisciplinary field limited dominantly by their scarce availability. In this work, radioactive molecular ion beams containing actinide nuclei extracted from uranium carbide targets are produced via the Isotope Separation On-Line technique at the CERN-ISOLDE facility. Two methods of molecular beam production are studied: extraction of molecular ion beams from the ion source, and formation of molecular ions from the mass-separated ion beam in a gas-filled radio-frequency quadrupole ion trap. Ion currents of U+, UO1−3+, UC1−3+, UF1−4+, UF1,2O1,2+are reported. Metastable tantalum and uranium fluoride molecular ions are identified. Formation of UO1−3+, U(OH)1−3+, UC1−3+, UF1,2O1,2+from mass-separated beams of U+, UF1,2+with residual gas is observed in the ion trap. The effect of trapping time on molecular formation is presented.

ISOLDE’s Offline 2 laboratory has been upgraded to facilitate development for the production and study of molecular ion beams. New gas injection systems have been implemented for both molecular formation in the ion source and in the radio-frequency quadrupole ion trap used for beam preparation. MagneToF detectors and time-resolved single ion counting data acquisition have been implemented for low intensity beams and studies of laser-atom or laser-molecule interactions. We present a study of the formation and ionization of BaF+using the upgraded facility.

Relativistic coupled-cluster calculations of the ionization potential, dissociation energy, and excited electronic states under 35,000 cm$^{-1}$ are presented for the actinium monofluoride (AcF) molecule. The ionization potential is calculated to be IP$_e=48,866$ cm$^{-1}$, and the ground state is confirmed to be a closed-shell singlet and thus strongly sensitive to the $\mathcal{T}$,$\mathcal{P}$-violating nuclear Schiff moment of the Ac nucleus. Radiative properties and transition dipole moments from the ground state are identified for several excited states, achieving an uncertainty of $\sim$450 cm$^{-1}$ for the excitation energies. For higher-lying states that are not directly accessible from the ground state, possible two-step excitation pathways are proposed. The calculated branching ratios and Franck-Condon factors are used to investigate the suitability of AcF for direct laser cooling. The lifetime of the metastable $(1)^3\Delta_1$ state, which can be used in experimental searches of the electric dipole moment of the electron, is estimated to be of order 1 ms.

Molecules containing short-lived, radioactive nuclei are uniquely positioned to enable a wide range of scientific discoveries in the areas of fundamental symmetries, astrophysics, nuclear structure, and chemistry. Recent advances in the ability to create, cool, and control complex molecules down to the quantum level, along with recent and upcoming advances in radioactive species production at several facilities around the world, create a compelling opportunity to coordinate and combine these efforts to bring precision measurement and control to molecules containing extreme nuclei. In this manuscript, we review the scientific case for studying radioactive molecules, discuss recent atomic, molecular, nuclear, astrophysical, and chemical advances which provide the foundation for their study, describe the facilities where these species are and will be produced, and provide an outlook for the future of this nascent field.

Thursday 14 April 2022 Contribution X-O41 Chair: E. Colineau

Contribution ID:57 Type:Invited Tuesday, December 14, 2021 2:40 PM (15 minutes)