COULOMB LINE VACUUM POLARIZATION CORRECTIONS TO LAMB SHIFT OF ORDER ALPHA(2)(Z-ALPHA)(5)M

Radiative corrections of order alpha2(Zalpha)5m to the Lamb shift are considered. It is shown that all contributions of this order are induced by six gauge invariant sets of diagrams with two external Coulomb lines and different radiative insertions. Corrections connected with diagrams containing polarization insertions in external Coulomb lines are calculated and their contribution is equal to 0.056 [alpha2(Zalpha)5/pi]m for the hydrogen state with principal quantum number of two. This gives 2.42 kHz as a correction.