content_image/345498.jpg
<img src='content_image/345498.jpg'>

SMS values from the related results by other nonrelativistic calculations, we estimate an uncertainty associated with the electron correlation as 0 . 05% for lithium, 0 . 002% for Li-like boron and much less for ions with larger nuclear charge numbers. 

One-electron and two-electron QED recoil corrections were calculated in accordance with our previous works [36, 37, 47]. The evaluation is performed for extended nuclei within the approximation of noninteracting electrons. The electron-electron interaction is suppressed by a factor 1 /Z , therefore we estimate the uncertainty of the QED recoil contribution mul- tiplying it by 1 /Z . 

As one can see, in the case of Li our values agree well with the previous theoretical predictions [35, 39–44] as well as with the experimental data [45, 46]. 

In Fig. 1 we plot the individual contributions to the MS coefficient K for the 2 p$_{1}$$_{/}$$_{2}$ − 2 s and 2 p$_{3}$$_{/}$$_{2}$ − 2 s transitions in Li-like ions. The dotted line indicates the relative contribution of the electron-electron interaction; the dashed line represents the relativistic correction; and the dashed-dotted line stands for the QED part of the coefficient. We observe that for low- Z ions it is extremely important to include the electron-electron interaction effects. 

