The coupled-channel method is used to calculate single-, and double-ionisation cross sections for helium collisions with heavy ions. For highly charged and slow projectiles where the ratio of the projectile charge divided by the projectile velocity is in the magnitude of unity, non-perturbative methods must be used for proper description of the physical process.
As basis functions Slater-like orbitals and regular Coulomb wave packages were taken. The Coulomb wave packages give a satisfactory approximation of the single and double electron continua, which is needed to reach convergence for the cross sections.
As Electron-Projectile interaction the Liénard-Wiechert- Potentials were used minimal coupled to the impulse operator of the electron. The projectile was considered as a classical point-like charge ying on a straight line.
12 different calculations were done for different heavy ions from proton up to U92+ and compared with experimental data.
