Electron correlation in high energy double ionization of helium by Compton scattering

We report new results of calculations for double ionization of helium by high energy Compton scattering. Our calculation is based on a recently developed perturbative approach, which describes the process in terms of two amplitudes: the shake off (SO) amplitude which includes all initial state correlations and final state interaction (FSI) amplitude. The shake amplitude is based on sudden approximation, and we evaluate the amplitude using highly correlated ground state wave function. The FSI amplitude includes Coulomb interaction between the ejected electrons perturbatively. We present the energy dependence of R, the ratio of the double to single ionization cross-section in the energy range of 30–200 keV of the incident photon energy. We obtain R = 0.82 % at the asymptotic energy of 200 keV. In the range from 30 to 80 keV the superposition of the shake and FSI amplitude gives the energy dependence of R which agrees very well with the experimental data. We present also the calculation of doubly differential cross-section with respect to the slow ejected electron energy and angle between ejected electrons.