Mean recoil-ion and electron longitudinal momentum in He single ionizationby proton and antiproton impact

We report CDW-EIS theoretical calculations of mean recoil-ion and electron longitudinal momentum in He single ionization by proton and antiproton impa ct as a function of the impact energy from 50 keV to 1 MeV. At intermediate energies the mean momenta of both electron and recoil ion are significativ ely different for proton and antiproton impact. At larger energies mean val ues for proton and antiproton cases approach one another as the Born approx imation turns out to be valid.