QED mα7 effects for triplet states of heliumlike ions

We perform ab initio calculations of the QED effects of order m alpha 7 for the 2 3S and 2 3P states of He-like ions. The computed effects are combined with previously calculated energies [V. A. Yerokhin and K. Pachucki, Phys. Rev. A 81, 022507 (2010)], thus improving the theoretical accuracy by an order of magnitude. The obtained theoretical values for the 2 3S-2 3P0,2 transition energies are in good agreement with available experimental results and with previous calculations performed to all orders in the nuclear binding strength parameter Z alpha. For the ionization energies, however, we find some inconsistency between the Z alpha-expansion and all-order calculations, which might be related to a similar discrepancy between the theoretical and experimental results for the ionization energies of helium [V. Patkos et al., Phys. Rev. A 103, 042809 (2021)].

Automated summary

We performed ab initio calculations of the QED effects for the 2 3S and 2 3P states of He-like ions at the order of m alpha 7. By combining the computed effects with previously calculated energies, the theoretical accuracy has been improved significantly. The obtained results for the transition energies agree well with experiment and previous calculations, while some inconsistency is observed for the ionization energies, possibly related to the theoretical-experimental discrepancy in helium ionization energies.