Effects of an Oscillating Electric Field on and Dipole Moment Measurement of a Single Molecular Ion

We characterize and model the Stark effect due to the radio-frequency (rf) electric field experienced by a molecular ion in an rf Paul trap, a leading systematic in the uncertainty of the field-free rotational transition. The ion is deliberately displaced to sample different known rf electric fields and measure the resultant shifts in transition frequencies. With this method, we determine the permanent electric dipole moment of CaH+, and find close agreement with theory. The characterization is performed by using a frequency comb which probes rotational transitions in the molecular ion. With improved coherence of the comb laser, a fractional statistical uncertainty for a transition line center of as low as 4.6 x 10-13 was achieved.

Automated summary

We study the Stark effect in an rf Paul trap to investigate its influence on the uncertainty of field-free rotational transition in a molecular ion. By measuring the changes in transition frequencies under known rf electric fields, we determine the permanent electric dipole moment of CaH+ and find agreement with theory. The rotational transitions in the molecular ion are probed using a frequency comb, with significantly improved coherence achieving a fractional statistical uncertainty as low as 4.6 x 10-13 for a transition line center.