Magnetic hyperfine structure constants of $^{137}$BaF in the $^2\Pi_{1/2}$ and $^2\Pi_{3/2}$ excited states

TL;DR

This paper calculates hyperfine structure constants of $^{137}$BaF in excited states using relativistic coupled-cluster methods, aiding precision experiments testing fundamental physics.

Contribution

It provides highly accurate hyperfine constants for $^{137}$BaF's excited states, incorporating relativistic effects and basis set extrapolation, which were previously unavailable.

Findings

Calculated hyperfine constants with estimated uncertainties.

Analyzed effects of basis sets and electron correlation.

Results support experimental spectroscopy and laser-cooling schemes.

Abstract

High-precision molecular experiments testing the Standard Model of particle physics require an accurate understanding of the molecular structure at the hyperfine level, both for the control of the molecules and for the interpretation of the results. In this work, we calculate the hyperfine structure constants for the excited states $^2\Pi_{1/2}$ and $^2\Pi_{3/2}$ of $^{137}$BaF due to the $^{137}$Ba nucleus. We use the 4-component relativistic Fock-space coupled-cluster method, extrapolating our results to the complete basis set limit. We investigate the effect of the basis sets and electron correlation, and estimate the uncertainty in our final results. Our results are used in the interpretation of the experimental spectroscopy of the hyperfine and rovibrational spectra of BaF, and the planning of laser-cooling schemes for future parity-violating anapole moment measurements [1].