Long coherence time of the JILA Generation III eEDM experiment

The recently concluded JILA experiment using HfF⁺ reported the most precise measurement yet of the electric dipole moment of the electron (eEDM), d_e = (-1.3 ± 2.0_stat ± 0.6_syst) × 10^-30 e cm, using electrons confined inside molecular ions [1,2]. The third-generation apparatus at JILA aims to push the limit even more, by taking advantage of the long coherence time of the eEDM-sensitive state (³Δ₁) of ThF⁺, which is the ground state [3,4,5]. We measure a coherence time of about 8 seconds in our prototype experiment, and report the limiting factors for the coherence time, including blackbody radiation, rotating electric field inhomogeneity, ion-neutral collisions, and ion-ion collisions.

[1] Roussy, Tanya S. et al. Science 381, 46-50(2023).

[2] Caldwell, Luke, et al. Phys. Rev. A 108.1 (2023): 012804.

[3] Gresh, Daniel N. et al. Journal of Molecular Spectroscopy 319 (2016): 1-9.

[4] Zhou, Yan et al. J. Mol. Spec. 358, (2019) 1-16.

[5] Ng, Kia Boon et al. Phys. Rev. A 105, 022823.