Rotational spectroscopy of a single molecular ion at sub part-per-trillion resolution

TL;DR

This paper demonstrates ultra-precise rotational spectroscopy of a single molecular ion using quantum-logic techniques and frequency combs, achieving unprecedented resolution and enabling accurate electric dipole moment measurement.

Contribution

It introduces a novel application of quantum-logic spectroscopy combined with frequency combs for high-resolution rotational spectroscopy of a single molecular ion.

Findings

Achieved a fractional uncertainty of 4 x 10^-13 in transition line center measurement.

Improved Stark effect resolution in a Paul trap environment.

Determined the electric dipole moment of CaH+ with high precision.

Abstract

We use quantum-logic spectroscopy (QLS) and interrogate rotational transitions of a single CaH+ ion with a highly coherent frequency comb, achieving a fractional statistical uncertainty for a transition line center of 4 x 10^-13. We also improve the resolution in measurement of the Stark effect due to the radio-frequency (rf) electric field experienced by a molecular ion in an rf Paul trap, which we characterize and model. This allows us to determine the electric dipole moment of CaH+ by systematically displacing the ion to sample different known rf electric fields and measuring the resultant shifts in transition frequency.