Precision Measurement of the Electron's Electric Dipole Moment Using Trapped Molecular Ions

We describe the first precision measurement of the electron's electric dipole moment (d_e) using trapped molecular ions, demonstrating the application of spin interrogation times over 700 ms to achieve high sensitivity and stringent rejection of systematic errors. Through electron spin resonance spectroscopy on ¹⁸⁰Hf ¹⁹F⁺ in its metastable ³Δ₁ electronic state, we obtain d_e=(0.9 ±7. 7_stat±1. 7_syst)×10^-29 e cm , resulting in an upper bound of |d_e|<1.3 ×10^-28 e cm (90% confidence). Our result provides independent confirmation of the current upper bound of |d_e|<9.4 ×10^-29 e cm [J. Baron et al., New J. Phys. 19, 073029 (2017), 10.1088/1367-2630/aa708e], and offers the potential to improve on this limit in the near future.