Charge asymmetry of ionization cross sections of atomic hydrogen by antiproton and proton impact

Large-scale coupled-channel calculations are carried out for the evaluation of the ionization cross section of atomic hydrogen by antiproton impact. The dependence of the ionization cross sections on the projectile charge is investigated in comparison with the case of proton impact. It is demonstrated that continuum states of the antiproton, which were not taken into account satisfactorily in previous calculations, play an important role for the ionization. The ionization cross section ratio of the antiproton and proton impact obtained by the present coupled-channel calculations is close to the classical trajectory Monte Carlo (CTMC) value at variance with the result of Ermolaev. (orig.)