Compton ionization of hydrogen atom near threshold by photons in the energy range of a few keV: nonrelativistic approach

Recently, there have been published the results of unique experiments on measuring the fully differential cross sections of the Compton single ionization of the helium atom near the ionization threshold at a photon energy of a few keV. This opens up a possibility of using Compton ionization along with the ionization of atoms/molecules by fast charged particles to study characteristics of the ionization processes in more detail, since photons are neutral particles. In this regard, the paper deals with the ionization cross sections of the reaction (γ, γe) at the hydrogen atom, because the theoretical description of this reaction at the hydrogen atom does not need to consider a number of additional assumptions and approximations inherent in heavier atoms. Special attention is paid to the study of the kinematic region of the reaction near threshold, where it is expected to obtain a valuable information about the initial and final states of the target. The contribution of corrections to the first Born approximation due to the electron boundness is also discussed.