Broadband velocity modulation spectroscopy of ThF$^+$ for use in a measurement of the electron electric dipole moment

TL;DR

This study provides detailed spectral data and state characterization of ThF$^+$ ions, crucial for enhancing the sensitivity of electron electric dipole moment measurements in upcoming experiments.

Contribution

It offers comprehensive survey spectroscopy and precise molecular constants for ThF$^+$, identifying the eEDM-sensitive ground state and excited states for experimental use.

Findings

ThF$^+$ ground state is $X$ $^3\Delta_1$

High-precision rotational and vibrational constants determined

Spectral coverage of 700-1000 nm with frequency comb velocity modulation spectroscopy

Abstract

A number of extensions to the Standard Model of particle physics predict a permanent electric dipole moment of the electron (eEDM) in the range of the current experimental limits. Trapped ThF$^+$ will be used in a forthcoming generation of the JILA eEDM experiment. Here, we present extensive survey spectroscopy of ThF$^+$ in the 700 - 1000 nm spectral region, with the 700 - 900 nm range fully covered using frequency comb velocity modulation spectroscopy. We have determined that the ThF$^+$ electronic ground state is $X$ $^3\Delta_1$, which is the eEDM-sensitive state. In addition, we report high-precision rotational and vibrational constants for 14 ThF$^+$ electronic states, including excited states that can be used to transfer and readout population in the eEDM experiment.