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Prospects for assembling ultracold radioactive molecules from laser-cooled atoms



Jacek Klos, Hui Li, Eite Tiesinga, Svetlana Kotochigova


Molecules with unstable isotopes often contain heavy and deformed nuclei and thus possess a high sensitivity to parity-violating effects, such as Schiff moments. Currently the best limits on Schiff moments are set with diamagnetic atoms. Polar molecules with quantum-enhanced sensing capabilities, however, can offer better sensitivity. In this work, we consider the prototypical $^223}$Fr$^107}$Ag molecule, as the octupole deformation of the unstable $^223}$Fr francium nucleus amplifies the nuclear Schiff moment of the molecule by two orders of magnitude relative to that of spherical nuclei and as the silver atom has a large electronegativity. To develop a competitive experimental platform based on molecular quantum systems, $^223}$Fr atoms and $^107}$Ag atoms have to be brought together at ultracold temperatures. That is, we explore the prospects of forming $^223}$Fr$^107}$Ag from laser-cooled Fr and Ag atoms. We have performed fully relativistic electronic-structure calculations of ground and excited states of FrAg that account for the strong spin-dependent relativistic effects of Fr and the strong ionic bond to Ag. In addition, we predict the nearest-neighbor densities of magnetic-field Feshbach resonances in ultracold $^223}$Fr+$^107}$Ag collisions with coupled-channel calculations. These resonances can be used for magneto-association into ultracold, weakly-bound FrAg. We also determine the conditions for creating $^223}$Fr$^107}$Ag molecules in their absolute ground state from these weakly-bound dimers via stimulated Raman adiabatic passage using our calculations of the relativistic transition electronic dipole moments.
New Journal of Physics


precision measurements, laser cooling, parity violation, francium, silver


Klos, J. , Li, H. , Tiesinga, E. and Kotochigova, S. (2022), Prospects for assembling ultracold radioactive molecules from laser-cooled atoms, New Journal of Physics, [online],, (Accessed June 7, 2023)
Created February 21, 2022, Updated November 29, 2022