Core level binding energy shifts between free and condensed atoms

Assuming a fully screened final state (in the metallic case) and using the (Z + 1) approximation and a Born—Haber cycle we calculate the shift in the core level binding energy between the free atom and its metallic state. The agreement with known experimental shifts is shown to be very good. Utilization of the present method can for example give accurate core level binding energies for those free atoms where such data only exist for the metallic phase.