Formation of ions by high energy photons

We calculate the electron energy spectrum of ionization by a high energy photon, accompanied by creation of e − e + pair. The total cross section of the process is also obtained. The asymptotics of the cross section does not depend on the photon energy. At the photon energies exceeding a certain value !0 this appeares to be the dominant mechanism of formation of the ions. The dependence of !0 on the value of nuclear charge is obtained. Our results are consistent with experimental data.