Double excitation of He by multiply charged ions

We have studied double excitation of He by 1.5 MeV/amu protons, antiprotons, He2+, Li3+, C6+ and F9+, and 500 keV/amu He2+ and Li3+. For this purpose we have performed single-centre close-coupling calculations which allow for a simultaneous description of double excitation, ionization and, therefore, coherence between these processes. We have analysed the validity of the Born series to provide the cross section dependence on the projectile charge Zp. In particular, we show that, at 1.5 MeV/amu, the Born II approximation describes reasonably well excitation to the 1Se(2s2), 1Po(2s2p) and 1De(2p2) resonances for Zp = -1 and Zp = 1. On the other hand, the Born II approximation fails in describing excitation to the 1Se and 1Po resonances for Z ≥ 2. (author)