QED Effects in Cu-Like Pb Recombination Resonances Near Threshold

In an electron-ion recombination study with ${\mathrm{Pb}}^{53+}$ dielectronic recombination resonances are found for as low as $\sim {10}^{-3\mathrm{}}–{10}^{-4\mathrm{}}\mathrm{eV}$ relative energy. The resonances have been calculated by relativistic many-body perturbation theory and through comparison with experiment the ${\mathrm{Pb}}^{53+}\left({4p}_{1/2}-{4s}_{1/2}\right)$ energy splitting of $\sim 118\mathrm{eV}$ is determined with an accuracy comparable to the position of the first few resonances, i.e., $\sim {10}^{-3\mathrm{}}\mathrm{eV}$. Such a precision provides a test of QED in a many-body environment at a level which can still not be reached in calculations.