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Classical phase-space models of the hydrogen molecule and helium are utilized to study shell and subshell electron-capture processes in collisions of fully stripped ions on charge states from 1 to 15 with H{sub 2} and He at intermediate impact energies (20--200 keV/amu). Autoionization after double electron capture is approximated and is found to be an important channel for high projectile charges. The resulting ({ital n},{ital l}) distributions for proton impact of He and H{sub 2} as well as total capture cross sections are found to be in very good agreement with experimental data. {ital l} distributions for high projectile charges are also analyzed for {ital n} levels for which autoionization is negligible. It is found that electrons are captured preferentially to large {ital l} values.

Doubly and singly differential cross sections for electron emission have been calculated by means of the classical trajectory Monte Carlo method for the p/sup +/, p/sup -/, and He/sup 2+/+He systems at impact energies of 50 and 100 keV/amu. The calculations for the p/sup +/ and He/sup 2+/+He systems exhibit the capture to the continuum peak and agree in both shape and magnitude with experimental data. Analysis of the classical trajectories has helped to understand the dynamical formation of this peak. The dependence of the cross sections on the projectile charge (-1, +1, and +2) is analyzed and compared with first-order scalings. It is concluded from this analysis that the combined influence of both the projectile and target Coulomb fields prevails over all the electronic spectra.