A possible effect of the low photon density states in plasma on Lamb shift is analysed. It found that because a significant contribution high-energy virtual photons to shift, its modification does not exceed 1 % with respect vacuum even at electron concentrations as high 10 22 cm –3 . This behavior results from an asymptotic tendency properties ones unlimited frequency growth.

In muonic atoms the Uehling potential (an effect of a free electronic vacuum polarization loop) is responsible for the leading contribution to the Lamb shift causing the splitting of states with ∆n = 0 and ∆l 6= 0. Here we consider the Lamb shift in the leading nonrelativistic approximation, i.e., within an approach based on a certain Schrödinger equation. That is valid for low and medium Z as ...