On the distribution of electrons in the double ionization of helium-like ions by Compton scattering

The Compton scattering of a high energy photon by a helium-like ion, followed by the ionization of two electrons, is considered outside of the Bethe surface of Compton scattering with the knock-out of a single electron. The role of shake-off (SO), of final state interactions (FSI) and of the quasi-free mechanism (QFM) is analysed. The triple and double differential distributions are calculated. It is demonstrated for the first time that in certain kinematical regions the process is dominated by the FSI and by the QFM, while the SO contribution is much smaller.