Double atomic photoeffect in the relativistic domain: angular and energy distributions of photoelectrons

We study the double ionization of the atomic K-shell by a single photon in the relativistic energy domain. The differential and total cross sections of the process are calculated. It is shown that the ratio of the cross sections of double and single ionization increases with the photon energy, tending to the limit 0.34/Z2, where Z is the atomic number or the nuclear charge. The formulas are found to be valid for Z>>1 and αZ<<1, where α=1/137 is the fine-structure constant