Single and double ionization of helium in heavy-ion impact

We present single- and double-ionization total cross sections for collisions of helium atoms with multiple charged ions. In our study we apply two different approaches, namely the ab initio coupled channel and the classical trajectory Monte Carlo (CTMC) method. We consider bare projectiles with charge states between two and eight with energies between 0.19 and 2.31 MeV/amu. We find that our coupled-channel calculations are very close to the experimental data even for the case when the Coulomb fields are strong. At the same time CTMC models, using different independent-particle approximations, show somewhat larger discrepancies compared to the experimental cross sections. We also present cross sections for 1.44 MeV/amu O q + ( q = 4–7) projectiles.