Abstract. We have performed calculations for collisions between fully stripped ions, C 6+ and N 7+ , and atomic hydrogen, in both its ground and first excited energy levels. We have employed the Classical Trajectory Monte Carlo method to obtain total ionization and charge exchange cross sections and state selective charge exchange cross sections in the 5-500 keV/amu energy range.

A classical description of electron emission differential ionization cross sections for highly-charged high-velocity ions (∼ 10 a.u.) impinging on water molecules is presented. We investigate the validity of the classical statistical mechanics description of ionization ( = 0 limit of quantum mechanics) in different ranges of electron emission energy and solid angle, where mechanisms such as soft and binary collisions are expected to contribute. The classical-trajectory Monte Carlo method is employed to calculate doubly and singly differential cross sections for C 6+ , O 8+ and Si 13+ projectiles, and comparisons with Continuum Distorted Wave Eikonal Initial State theoretical results and with experimental data are presented. We implement a time-dependent screening effect in our model, in the spirit of mean-field theory to investigate its effect for highly charged projectiles. We also focus on the role of an accurate description of the molecular target by means of a three-center potential to show its effect on differential cross sections. Very good agreement with experiments is found at medium to high electron emission energies.

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We propose a classical trajectory Monte Carlo method to describe two-center collisions with two active electrons. The approach is based on switching between standard four-body and three-body descriptions and it is therefore easy to implement. We demonstrate the reliability of the approach for fundamental H+H and H + +H − collisions that neither four-body nor three-body classical methods describe satisfactorily.

Charge-transfer n partial cross sections have been calculated for collisions of Be 4+ with H(1s) by means of a versatile lattice method that is applicable in a wide energy range (between 1 and 500 keV/u). The cross sections, which include up to the high-lying n = 8 level, are compared to existing semiclassical calculations in order to quantify the accuracy of the results. The reliability of the lattice method at high impact energies is confirmed by comparison with classical trajectory Monte Carlo calculations. It is found that the n partial cross sections larger than 10 −18 cm 2 , calculated using the lattice method, agree with differences smaller than 15% with those from the method considered the most accurate at each energy. The calculation yields as well accurate total electron capture cross sections, which are studied in detail at E = 100 keV/u to obtain a converged value.