Analytical evaluation of cross sections for double ionization of heliumlike ions by high-energy-photon scattering

Double $K$-shell ionization of two-electron ions in Compton scattering of high-energy photons is investigated. The problem is treated analytically within the framework of nonrelativistic perturbation theory with respect to the interelectron interaction, using the Coulomb Green's and wave functions. The energy distribution of ejected electrons and the double-to-single cross section ratio are cast in the form of the universal scalings. The approximations made in previous theoretical works are discussed. Atomic targets are assumed to be characterized by moderate values of the nuclear charge number $Z$.

Figure 1

Feynman diagram describing the double Compton ionization of the $K$ shell. Solid lines denote electrons in the Coulomb field of the nucleus, the dashed line denotes the interelectron interaction, and wavy lines denote incident and scattered photons. The electron propagator with dot corresponds to the Coulomb Green's function.

Figure 2

Universal function $J\left({\varepsilon }_2\right)$ vs the dimensionless energy ${\varepsilon }_2$.