Abstrakt
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)].