Evaluation of the two-photon exchange diagrams for the (1s)22p3/2(1s)^2 2p_{3/2} electron configuration in Li-like ions

We present ab initio calculations of the complete gauge-invariant set of two-photon exchange graphs for the $(1s)^2 2p_{3/2}$ electron configuration in Li-like ions. These calculations are an important step towards the precise theoretical determination of the $2p_{3/2}$-$2s$ transition energy in the framework of QED.Comment: 17 pages, 6 figure