Contribution of higher order effects to the $(e,2e)$ process on the hydrogen atom

The physical series of the perturbation theory is defined for the case of multiparticle Coulomb scattering and the results of numerical calculations are given for the contribution of higher Born terms to the amplitude of the electron-induced quasielastic knockout of an electron from the hydrogen atom. The purpose is to find the range of applicability of the basic theory of such reactions.