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Description
High precision variational calculations in Hylleraas coordinates are presented for all singlet and triplet $P$-states of helium up to principal quantum number $n = 35$ with a uniform accuracy of 1 part in $10^{22}$ for the nonrelativistic energy. Mass polarization, relativistic and quantum electrodynamic effects are included to achieve a final accuracy of $\pm$1 kHz or better for the ionization energy of the Rydberg states of $^4$He in the range $24\le n \le 35$. The results are combined with 11 transition frequency measurements of Clausen et al.\ Phys.\ Rev. A 111, 012817 (2025) to obtain complementary measurements of the ionization energy of the $1s2s\;^3S_1$ state that do not depend on quantum defect extrapolations to the series limit. The result from the triplet spectrum yields an ionization energy of 1152\,842\,742.728(6) MHz, which agrees with but is larger than the experimental value by 14 $\pm$17 kHz. However, it confirms a much larger 9$\sigma$ discrepancy of $0.468\pm0.055$ MHz with the theoretical ionization energy of Patkos et al. Phys. Rev. A 103, 042809 (2021). The results provide a test of the quantum defect extrapolation method at the level of $\pm$17 kHz [1].
[1] G.W.F. Drake, A.T. Bondy, O.P. Hallett and B.C. Najem, Phys. Rev. A 113, 012810 (2026).
| Keyword-1 | helium atomic theory |
|---|---|
| Keyword-2 | Rydberg states |
| Keyword-3 | precision tests |