Electron capture, ionisation and transfer-ionisation in fast Auq++He collisions

Abstract

Cross sections for single electron capture and ionisation, as well as for simultaneous capture and ionisation ('transfer ionisation') are calculated for collisions of partially stripped Auq+ (q=6-25) ions with He atoms at collision energies between 20 and 300 keV amu-1 by using the classical-trajectory Monte Carlo method. The helium ion core has been represented by an effective charge Zeff(He)=1.69, while the electron interaction with the projectile ion has been described by a variable-charge potential. The calculated capture cross sections are in close agreement with the available experimental data, while the ionisation cross sections are consistent with them except for 10<or=q<or=16, where the authors' results at 100 keV amu-1 are too small by about a factor of two. The authors give the calculated energy dependence of the total cross sections and for electron capture the distribution of captured electrons among final n states, as well as their impact parameter distribution.