The electron screening effect in muonic 28Si

We have measured the wavelengths of the 4fsub(7/2)-3dsub(5/2) and the 4fsub(5/2)-3dsub(3/2) X-ray transitions in μ-28Si with the bent-crystal spectrometer at the SIN muon channel. The results are compared to the calculated transition wavelengths which include radiative corrections (QED). The differences in the corresponding transition energies are attributed to the electron screening shift. Combining the results from both transitions, we obtain ΔEsub(ES)(4f-3d) = -1.66 +- 0.20 eV. This corresponds to (83 +- 11)% of the electron-screening shift calculated for a neutral atom with the muon and Z - 1 electrons. These results are in moderate agreement with cascade calculations constrained to reproduce measured muonic X-ray intensities. (orig.)