Distortion effects in electron excitation of hydrogen atoms by impact of heavy ions

Electron excitation from the fundamental state of hydrogen atoms by impact of bare ions is studied at intermediate and high collision velocities. Total cross sections for final np states by impact of protons, alpha particles, and He⁺ ions are calculated using the symmetric eikonal approximation and compared with experimental data. This comparison supports the existence of distortion effects recently predicted by Bugacov and co-workers [Phys. Rev. A 47, 1052 (1993)]. The validity of scaling laws is analyzed.