Signatures of target<i>e</i>-<i>e</i>correlations in the angular distribution of (<i>e</i>,3<i>e</i>) differential cross sections for the ionization of helium by fast electrons

Abstract

The effect of target e-e correlations on the angular distribution of fivefold differential cross section for the double ionization of helium by fast electrons has been studied. The helium ground-state wave functions due to Byron and Joachain [Phys. Rev. 146, 1 (1966)], Silverman, Platas, and Matsen [J. Chem. Phys. 32, 1402 (1960)], and Tweed and Langlois [J. Phys. B 20, 5213 (1987)] have been employed. The calculation has been done in the first-order Born approximation with the two ejected electrons being described by a product of two Coulomb waves. The correlations in the final state have been accounted for by suitable effective charges and the Gamow correlation factor. Kinematics corresponding to or close to the Bethe ridge and with small momentum transfer and low ejected electron energies has been chosen. When one (energetic of the two) of the electrons is ejected along the momentum transfer direction, the angular distribution of the other for angles in the range 180\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}60\ifmmode^\circ\else\textdegree\fi{} with respect to the first is found to bear clear signatures of e-e correlations in the ground-state wave function. \textcopyright{} 1996 The American Physical Society.