Importance of the non-resonant corrections for the modern Lamb shift measurements in the multicharged hydrogen-like ions

The level of accuracy reached in the recent Lamb shift measurements for the multicharged ions requires the introduction of the non-resonant corrections which take into account the deviation of the natural line profiles from the simple Lorentz form. The frequency omega _max, corresponding to the maximum of the frequency distribution, differs from the energy difference Delta E: omega _max,= Delta E+ delta , where delta is the non-resonant correction. The value of delta , calculated for the process 2s+ gamma to 2_P3/2 to 1s+ gamma ' used recently for the Lamb shift measurement in hydrogenic phosphorus, is delta =-4.47*10^-5 eV, while the measured transition energy is: Delta E=EZ_P3/2-E_2s=2.23133(12) eV. This means that the correction delta becomes noticeable. However, the 2s-2_P1/2 energy shift measured in Li-like uranium is not affected by this correction.