Figure 2. Feynman diagrams representing the screened SE ( a − c ) and VP ( d − f ) corrections in the extended Furry representation. The wavy line indicates the photon propagator, the triple line displays the electron propagators in the effective potential, and the double line indicates the electron propagators in the Coulomb field of the nucleus. The symbol ⊗ represents the extra interaction term associated with the local screening potential. We consider here only the diagrams contributing to the ionization energy of the valence state. It means that the one-electron core and core-core interaction diagrams are omitted in our consideration. The corresponding contribution from the SE screening diagrams can be written as Δ E ( b ) a scrSE = Δ E (0) scrSE + Δ E (1 , irr) scrSE + Δ E (1 , red) scrSE + Δ E (1 , ver) scrSE . (17) 24 ( a ) − ( b ) − × ( c ) − × ( d ) − ( e ) − × ( f ) − ×