Experimentally determined energy shifts of the electronic $K$ x rays in heavy muonic atoms are compared with calculations. These shifts may be caused by the incomplete screening of the nuclear charge by the muon and, in addition, by electron vacancies produced in higher shells by preceding Auger transitions. The first mechanism alone explains the experimental data within their uncertainties. This agreement and the absence of a noticeable difference between the shifts of the electronic $K\alpha$ and $K\beta$ x rays, show that the inner shells are essentially instantaneously refilled during the muonic cascade. Precision measurements of this type would give supplementary information on the initial muon distribution over $l$ states.

• Received 30 May 1980

DOI:https://doi.org/10.1103/PhysRevA.22.2081