QED calculation of ionization energies of $1snd$ states in helium

TL;DR

This paper performs advanced QED calculations of ionization energies for helium's $1snd$ states, extending previous theory to include $m extalpha^6$ corrections and analyzing discrepancies with experimental data.

Contribution

It introduces the complete $m extalpha^6$ correction to helium ionization energies, revealing smaller effects than expected and analyzing deviations from measurements.

Findings

$m extalpha^6$ effects are smaller due to cancellations.

Confirmed deviations between theory and experiment for certain transitions.

Analyzed potential reasons for discrepancies.

Abstract

Quantum electrodynamical (QED) calculations of ionization energies of the $1snd\,D$ states are performed for the helium atom. We reproduce the previously known relativistic and QED effects up to order $m\alpha^5$ and extend the theory by calculating the complete $m\alpha^6$ correction. The total contribution of the $m\alpha^6$ effects is shown to be much smaller than previously estimated, due to a large cancelation between the radiative and non-radiative parts of this correction. As a result of our calculations, we confirm the previously reported deviations between measured transition energies and theoretical predictions for the $nD$--$2S$ and $nD$--$2P$ transitions. Possible reasons for this discrepancy are analyzed.