Laser-cooled HgF as a promising candidate to measure the electric dipole moment of the electron

In order to realize more sensitive measurement of the electron's electric dipole moment (eEDM), it would be worthwhile to find new laser-cooled molecules with large internal effective electric field (Eeff), high electric polarizability, and long lifetime of the eEDM measurement state. Here we demonstrate the theoretical feasibility of laser cooling and trapping the mercuric monofluoride (Hg202F19, X2Σ1/2) radicals, as well as their application in the eEDM measurement. We investigated the electronic, rovibrational, and hyperfine structures and verified the highly diagonal Franck-Condon factors of the main transitions by the Rydberg-Klein-Rees inversion method and the Morse approximation. Hyperfine manifolds of the X2Σ1/2(υ=0) rotational states were examined with the effective Hamiltonian approach and a feasible sideband modulation scheme was proposed. In order to enhance optical cycling, the microwave remixing method was employed to address all the necessary levels. The Zeeman effect and the hyperfine structure magnetic g factors of the X2Σ1/2(υ=0,N=1) state were studied subsequently. Finally, its statistical sensitivity for the eEDM measurement was estimated to be about 6×10-32ecm in the trap, indicating that Hg202F19 might be a promising laser-cooled eEDM candidate when compared with the most recent ThO result of de=(4.3±3.1stat±2.6syst)×10-30ecm [V. Andreev et al. (The ACME Collaboration), Nature (London) 562, 355 (2018)10.1038/s41586-018-0599-8].