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Toward collinear laser spectroscopy of radioactive molecules utilizing in-trap-produced molecular ion beam

W. C. Mei1, S. J. Chen1, X. F. Yang1,*, J. H. Lv2, D. Y. Chen1, H. R. Hu1, Y. F. Guo1, Z. Yan1, Y. P. Jing1 et al.

C. Zhang1, Y. P. Lin1, T. X. Gao1, X. Shen1, S. W. Bai3, R. F. Garcia Ruiz4, J. Yang2, and Y. L. Ye1

  • *Contact author: xiaofei.yang@pku.edu.cn
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Phys. Rev. Research 8, 033285 – Published 8 September, 2026

DOI: https://doi.org/10.1103/68s7-71qt

Abstract

Molecules containing short-lived isotopes, namely, radioactive molecules, are among the most promising candidates for probing new physics beyond the standard model, although their production and spectroscopic measurements remain technically challenging. Here, we demonstrate an integrated methodology that combines the formation of molecular ion beams in a radio-frequency quadrupole cooler-buncher with collinear laser spectroscopy. As a proof-of-principle experiment, we successfully produce molecular ions BaF+ and YbF+ via in-trap ion-molecule reactions and perform high-resolution laser spectroscopy of the target molecule BaF138. Vibrational and rotational structures of BaF138 molecules across different electronic states are obtained using resonance-enhanced multiphoton ionization schemes, confirming the feasibility of the proposed methodology. This work establishes a practical route for future formation and spectroscopic studies of short-lived radioactive molecules, such as those containing Ra225, at radioactive ion beam facilities.

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Phys. Rev. Research 8, 033285– Published 8 September, 2026
  • Received 16 March 2026
  • Accepted 11 August 2026
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