ANGULAR-DISTRIBUTIONS IN THE DOUBLE IONIZATION OF HELIUM BY ELECTRON-IMPACT

Electron-impact double ionization of helium is investigated theoretically for the case of high incident energies (5-10 keV). An ab initio calculation is proposed, which includes almost full correlation in the initial state and partial correlations in the final state. The results of this model are compared with those given by other theories in the framework of the wave-function approach. We show that the correlations in the final state must be taken into account for the evaluation of the angular distributions.