Measurement of the molecular dipole moment and the hyperfine and $\Lambda$-doublet splittings of the $B^3\Pi_1$ state of thallium fluoride

TL;DR

This study precisely measures the hyperfine structure, Stark shifts, and electric dipole moments of the $B^3\Pi_1$ state in thallium fluoride, providing data crucial for optical cycling and fundamental symmetry experiments.

Contribution

It presents the first high-precision measurements of hyperfine splittings, Stark shifts, and dipole moments in the $B^3\Pi_1$ state of thallium fluoride, aiding future quantum and fundamental physics research.

Findings

Permanent electric dipole moment of 2.28(7) D

Lambda-doublet splittings of 14.4(9) MHz and 17.4(11) MHz

Observation of Stark shifts in the $B^3\Pi_1$ state

Abstract

We report high-precision measurements on the thallium fluoride $\tilde{J} = 1$ hyperfine manifold of the $B^3\Pi_1$ ($\nu = 0$) state. This state is of special interest because it is central to an optical cycling scheme that is envisioned to play an important role in enhancing the sensitivity of the CeNTREX nuclear Schiff-moment experiment presently under construction. The measurements are made by monitoring the fluorescence induced by narrow-band laser excitation of a cryogenic molecular beam. We use a multipass arrangement of the laser beam to enhance fluorescence. When viewed with a camera, we can spatially resolve images from adjacent passes that approach the molecules from opposing directions. These images yield a sensitive visual method to identify the central frequency of a transition. Coupling these line-center determinations with frequency calibration from an acousto-optic modulator has allowed a more precise determination of the $\tilde{J} = 1$ manifold of hyperfine level splittings. We observe Stark shifts of the $\tilde{J} = 1$ levels and infer a permanent electric dipole moment of 2.28(7) D and $\Lambda$-doublet splittings for the $F_1' = 1/2$ and $F_1' = 3/2$ manifolds of 14.4(9) MHz and 17.4(11) MHz, respectively.