Comparison of muonic-atom and electronic x-ray isotope shifts in lead

New measurements by Lee and Boehm of electronic x-ray isotope shifts in lead substantially reduce, but do not eliminate, the discrepancy between electronic x-ray and muonic isotope shifts in this element. For the isotope pairs ${}_{}{}^{208-207}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{206-204}{}_{}{}^{}\mathrm{Pb}$, we confirm the conclusion of Lee and Boehm that electronic and muonic data are now consistent. For the isotope pair ${}_{}{}^{208-206}{}_{}{}^{}\mathrm{Pb}$, the reported electronic x-ray shift is less by at least 22% (2 standard deviations) than what would be expected on the basis of the muonic data. Internal inconsistencies in the muonic data for this pair of isotopes can be removed by postulating a nuclear resonance that pushes the $2p_{\frac{3}{2}}$ state up by 0.3 keV or the $2p_{\frac{1}{2}}$ state down by 0.3 keV. For the isotope pair ${}_{}{}^{208-204}{}_{}{}^{}\mathrm{Pb}$, the discrepancy between electronic and muonic data is in the same direction as for ${}_{}{}^{208-206}{}_{}{}^{}\mathrm{Pb}$, but it is somewhat smaller and may not be significant.

[NUCLEAR STRUCTURE ${}_{}{}^{208,207,206,204}{}_{}{}^{}\mathrm{Pb}$; analyzed muonic isotope shifts, compared electronic shifts.]