Two-photon exchange corrections to the 2p(1/2)-2s transition energy in Li-like high- Z ions

A rigorous QED calculation of the two-photon exchange corrections to the 2p(1/2)- 2s transition energy in Li-like high- Z ions is presented. The contribution due to an exchange by more than two photons is evaluated within the Breit approximation. The resulting theoretical value of the 2p(1/2)- 2s transition energy in Li-like uranium is found to be 280.44(20) eV.