Extrapolation of the Zα–Expansion and Two–Loop Bound–State Energy Shifts
نویسنده
چکیده
Quantum electrodynamic (QED) effects that shift the binding energies of hydrogenic energy levels have been expressed in terms of a semi-analytic expansion in powers of Zα and ln[(Zα)−2], where Z is the nuclear charge number and α is the fine-structure constant. For many QED effects, numerical data are available in the domain of high Z where the Zα expansion fails. In this Letter, we demonstrate that it is possible, within certain limits of accuracy, to extrapolate the Zαexpansion from the low-Z to the high-Z domain. We also review twoloop self-energy effects and provide an estimate for the problematic nonlogarithmic coefficient B60. PACS numbers: PACS: 12.20.Ds, 11.15.Bt, 11.10.Jj
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