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 (HfF+)-Hf-180-F-19 in its metastable (3)Delta(1) electronic state, we obtain d(e) = (0.9 +/- 7.7(stat) +/- 1.7(syst)) x 10(-29) e cm, resulting in an upper bound of |d(e)| < 1.3 x 10(-28) e cm (90% confidence). Our result provides independent confirmation of the current upper bound of |d(e)| < 9.4 x 10(-29) e cm [J. Baron et al., New J. Phys. 19, 073029 (2017)], and offers the potential to improve on this limit in the near future.