Speaker
Description
Recent measurements for the ionization energies of the Rydberg singlet-P and triplet-P states of helium for principal quantum number $n = 24$ to 100 [1] present a new challenge to high-precision atomic theory. A long-standing obstacle is that the accuracy of variational calculations for two-electron systems rapidly declines with increasing $n$. The problem has now become urgent with the publication of the Clausen et al. measurements. We will present new variational techniques that allow high-precision results to be extended as high as $n = 30$ [2], thereby setting a new record of accuracy for high-lying Rydberg states. The combination of theory and experiment provides absolute points of reference for transitions to lower-lying states where there is an $8\sigma$ disagreement between theory and experiment. Relativistic and quantum electrodynamic (QED) corrections are included by perturbation theory up to order $\alpha^5mc^2$. Higher-order QED uncertainties are strongly suppressed due to their $1/n^3$ scaling, thereby resulting in total theoretical uncertainties as low as $\pm$2 kHz.
[1] G. Clausen et al., Phys. Rev. A 111, 012817 (2025).
[2] A. Bondy et al., Phys. Rev. A 111, L010803 (2025).
| Keyword-1 | Atomic theory |
|---|---|
| Keyword-2 | Rydberg states |
| Keyword-3 | Relativistic and QED energy |
