Optical Spectroscopy of Tungsten Carbide for Uncertainty Analysis in Electron Electric Dipole Moment Search

TL;DR

This study uses laser spectroscopy on tungsten carbide molecules to evaluate their suitability for precise electron electric dipole moment measurements, focusing on hyperfine structure, systematic uncertainties, and experimental conditions.

Contribution

It provides detailed spectroscopic data and discusses an alternative measurement scheme to reduce systematic uncertainties in electron EDM searches using WC molecules.

Findings

Hyperfine structure and Omega-doublet measured

Potential systematic uncertainties estimated

Flux and temperature characterized for experimental optimization

Abstract

We perform laser induced fluorescence(LIF) spectroscopy on a pulsed supersonic beam of tungsten carbide(WC) molecules, which has been proposed as a candidate molecular system for a permanent Electric Dipole Moment(EDM) search of the electron in its rovibrational ground state of the X3Delta1 state. In particular, [20.6]Omega=2, v'=4 <- X3Delta1,v"=0 transition at 485nm was used for the detection. The hyperfine structure and the Omega-doublet of the transition are measured, which are essential for estimating the size of the potential systematic uncertainties for electron EDM measurement. For further suppression of the systematic uncertainty, an alternative electron EDM measurement scheme utilizing the g factor crossing point of the Omega-doublet levels is discussed. On the other hand, flux and internal temperature of the molecular beam are characterized, which sets the limit on the statistical uncertainty of the electron EDM experiment. With the given results, the prospect of electron EDM experiment with the X3Delta1 state of WC molecule is discussed.