Total cross sections for K-K electron transfer in fast ion-atom collisions: the impulse and strong potential Born approximations

For the first time the strong potential Born (SPB) and the impulse (IA) approximation for K-K electron capture are evaluated exactly using non-hydrogenic (Herman-Skillman) wavefunctions. It is shown that the long-range tail of the target nucleus potential leads to a loss of normalization of off-shell electronic wavefunctions and results in cross sections in disagreement with experiment. A wavepacket renormalization procedure restores agreement with experiment and for proton impact leads to cross sections close to those provided by the IA. However, for projectiles of higher charge, off-shell effects persist and the renormalized SPB cross sections are more accurate than those of the IA.