The Role of Electron Correlations in the Double Ionization
of Helium by Fast Protons

E. M. Lobanova^a, S. A. Sheinerman^a*, and L. G. Gerchikov^b

^a St. Petersburg State Maritime Technical University, St. Petersburg, 198262 Russia

^b St. Petersburg State Technical University, St. Petersburg, 195251 Russia

* e-mail: ssheiner@ss12686.spb.edu

Received February 6, 2007

Abstract—We consider the double ionization (DI) of a helium atom by fast protons and study the role of elec-
tron correlations in this process. We develop a quantum-mechanical approach that takes into account the inter-
action of the emitted electrons in continuum and the dynamical charge screening of the ejected particles, which
depends on their ejection kinematics. The interaction of the emitted electrons between themselves and with the
core is described in the model of approximate 3C functions, while the dynamical charge screening is described
by introducing effective charges of the emitted electrons and the ion core, which are determined by the particle
momenta. The derived closed analytical expressions for the differential ionization cross sections have been
applied to the case of a coplanar particle ejection geometry at various momenta q transferred to the atom. Anal-
ysis of our calculations has shown that the developed model describes adequately the available experimental
data. Including the dynamical charge screening has a significant effect on the DI cross section and improves
considerably the agreement between theory and experiment.

PACS numbers: 34.10.+x, 34.50.Fa

DOI: 10.1134/S1063776107090038

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