This paper presents the results of a precision re-evaluation of the $\mu$-mesonic x-ray transition energies for Tl, Pb, Bi, Ti, Fe, Cu, and Zn. The $2p-1s$ and $3d-2p$ transition regions were studied for Tl, Pb, and Bi, and the $2p$ fine structure splitting was determined with good precision from both sets of measurements. The Tl, Pb, and Bi transition energies were determined to about 0.2%, while the $2p$ state fine structure splitting was determined to within 2 to 3%. The results are in good agreement with the theoretically predicted values of Ford and Wills, based on the charge distributions implied from the high-energy electron scattering experiments. An anomaly in the observed intensity ratio of the $2p_{\frac{1}{2}}-1s$ to $2p_{\frac{3}{2}}-1s$ transitions for Bi and Tl is discussed. It is believed to be due to an excitation of the first excited state of the initial nucleus. The observed $2p-1s$ transition energies for Ti, Fe, Cu, and Zn are given, with experimental uncertainties of 0.2 to 0.3%. The comparison with the theoretically predicted values is much improved relative to the earlier experimental results.

• Received 1 June 1962

DOI:https://doi.org/10.1103/PhysRev.128.2360