Role of projectile continuum states in the ionization of atomic hydrogen by high-energy ion impact

Ionization of atomic hydrogen in collisions with H + and He 2+ ions is studied by a large-scale coupled-channel calculation. It is demonstrated that high-lying continuum states of the projectile, which have been disregarded in previous calculations, contribute significantly to the ionization of the target atom. The portion of the ionization into these projectile continuum states amounts to 13% of the total ionization cross section in the case of H + impact even in the MeV region, and the question is raised as to the normalization procedure of experimental values to the Born cross section there. The partial cross section of the ionization into the target continuum satisfies the Z 2 scaling rule (where Z is the projectile charge) at high energies while the component into the projectile continuum states has a weaker dependence on the charge.