Ionization of helium in positron impact

We present single-ionization cross sections of helium for positron impact within the framework of classical trajectory Monte Carlo (CTMC) method and compare with Coulomb distorted-wave models and experimental data. The incident positron energy was varied between the ionization threshold and 500 eV. Our results are in agreement with the experimental data. We also present ionization cross sections where the He+ ion remains either in the 1s ground state or is simultaneously excited into the 2s or 2p state.