Lamb Shift in Heliumlike Ions

Estimates of the Lamb shift in bound states of two-electron ions reported by Kastner are discussed critically. A consistent treatment of the quantum-electrodynamical correction of order ${\alpha }^3$ to the relativistic potentials of ionization of atoms with two electrons is developed and convenient expressions for these corrections in a $|nLSJ〉$ state of the atom are obtained. The numerical results are in close agreement with the experimental data of Edlén and Löfstrand for C v.