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High-resolution spectroscopy of barium monofluoride: Odd isotopologues, hyperfine structure, and isotope shifts

Felix Kogel1, Yuly Chamorro2, Mangesh Bhattarai3,4, Marian Rockenhäuser1,5, Tatsam Garg1,5, David DeMille3,4,6, Anastasia Borschevsky2, and Tim Langen1,5,*

  • *Contact author: tim.langen@tuwien.ac.at
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Phys. Rev. A 112, 042807 – Published 9 October, 2025

DOI: https://doi.org/10.1103/rdpt-99qy

Abstract

Barium monofluoride (BaF) is a promising molecular species for precision tests of fundamental symmetries and interactions. We present a combined theoretical and experimental study of BaF spectra and isotope shifts, focusing in particular on the poorly understood odd isotopologues BaF137 and BaF135. By comparing state-of-the-art ab initio calculations with high-resolution fluorescence and absorption spectroscopy data, we provide a benchmark for electronic structure theory and disentangle the hyperfine and rovibrational spectra of the five most abundant isotopologues, from BaF138 to BaF134. The comprehensive knowledge gained enables a King plot analysis of the isotope shifts that reveals the odd-even staggering of the barium nuclear charge radii. It also paths the way for improved laser cooling of rare BaF isotopologues and crucially supports future measurements of nuclear anapole and Schiff moments.

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See Also

Magnetic hyperfine structure constants of BaF137 in the Π1/22 and Π3/22 excited states

Yuly Chamorro, Felix Kogel, Tim Langen, and Anastasia Borschevsky
Phys. Rev. A 112, 042808 (2025)

Article Text

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Phys. Rev. A 112, 042807– Published 9 October, 2025
  • Received 3 July 2025
  • Accepted 2 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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