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There is a 10$\sigma$ discrepancy between theory and experiment for the ionization energy of the $1s2s^3S_1$ state of helium [1]. In order to provide an additional check, Clausen et al. [2] have performed measurements for the Rydberg $P$-states of helium from $n = 24$ to $n = 100$ and extrapolated to $n = \infty$ to find the ionization energy. In the present work, we extend previous high-precision variational calculations [3] up to $n = 24$ using triple basis sets in Hylleraas coordinates. With the inclusion of relativistic and QED corrections, the results provide a direct theoretical test against the Clausen measurement at $n = 24$. The results are in excellent agreement, thereby confirming the 10$\sigma$ discrepancy between theory and experiment for the ionization energy of the $1s2s^3S_1$ state of helium.
[1] V. Patkos, V. A. Yerokhin and K. Pachucki, Phys. Rev. A 103, 042809 (2021).
[2] G. Clausen et al. Phys. Rev. Lett. 127, 093001 (2021).
[3] G. W. F. Drake, M. M. Cassar and R. A. Nistor, Phys. Rev. A, 65, 054501 (2002).
| Keyword-1 | High-precision theory |
|---|---|
| Keyword-2 | Rydberg states in helium |
