Description
High-precision spectroscopy of atomic species provides a powerful means of testing quantum electrodynamics(QED) and its theoretical frameworks. Helium has one of the simplest atomic structures, and QED calculations for helium have advanced to include corrections up to order $m\alpha^7$ [1]. Consequently, precision spectroscopy of helium has become the focus of many groups worldwide [2-6]. At present, the $2^3S_1-$$2^3P$ transition in helium is calculated to an accuracy of $\sim1$ kHz [7]. By measuring this transition with sub-100 Hz precision and comparing the results with theoretical calculations, including corrections up to order $m\alpha^8$, we aim to perform a stringent test of QED. This measurement would also lead to the determination of the nuclear charge radius difference with much better accuracy. Furthermore, the availability of two stable helium isotopes enables a difference measurement through the isotope shift, allowing for an additional comparison with theory. In our lab, we aim to accurately measure the $2^3S_1-$$2^3P$ transition frequencies of both $^4$He and $^3$He using ultracold metastable helium atoms. The advantage of using ultracold clouds of helium atoms is that we will reduce a major error in the determination of the isotope shift, the first-order Doppler shift, that was present in all previous measurements. In this work, we will present our progress towards the construction of a precision absolute laser facility with sub-kHz resolution and experimental procedures to mitigate the systematic errors.
[1] V. Patkos et al., PRA 103, 042809 (2021)
[2] R. J. Rengelink et al., Nat.Phys 14, 1132-1137 (2018).
[3] X. Zheng et al., PRL 119, 263002 (2017).
[4] Y. van der Werf et al., Science 388, 850-853 (2025).
[5] G. Clausen et al., PRL 134, 223001 (2025).
[6] K. Steinbach et al., PRL 136, 243001 (2026).
[7] Wen et al., Sci.Adv 11, eadu9796 (2025).
| I am the presenting author | Yes |
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