Scattering correlation in double ionization of helium by fast antiprotons and protons

The difference between the double-ionization cross sections of antiprotons and protons colliding with helium may be explained by the distortion of the two-electron wave function during the collision. The distortion is related to the presence of electron-electron correlations and depends on the sign of the projectile charge. The proposed correlation effect requires an at-least-partly-adiabatic behavior for target electrons. The existence of adiabaticity in high-energy large-impact-parameter collisions is discussed. By building in the effect of distortion into the center-of-charge interaction formulation of the independent-particle model, the calculated cross sections are in agreement with the experimental values.