Influence of the effective charges on the five-fold differential cross section for ionization of hydrogen and helium

Five-fold differential cross sections for the ionization of hydrogen and helium have been calculated and in the case of helium compared with the experiments of Ehrhardt and co-workers (1972). It is shown that exchange and capture processes are relevant only for primary energies below 250 eV and 80 eV respectively. The two outgoing electrons are described by a product of Coulomb waves in which the charges are treated as parameters in order to simulate the screening of the residual ion. The different sets of effective charges yield results which greatly differ in the angular position of the binary encounter maximum and the ratio of intensities in the binary encounter and the recoil peak. The results indicate that it is more important to know the full wavefunction in the region where all particles are close together rather than to require fulfilment of the proper asymptotic conditions.

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