Abstract
The hydrogen ionization collision Hn-MB, where Hn is a hydrogen atom in state n and MB is the atom H, Li or Na and may be left in any final state, is considered. The Born approximation is used, together with an approximation to the sum over all final states of MB. Also, initially the ionized electron is treated in the plane-wave approximation and later the continuum Coulomb function is used. The results are given in the energy range 20-150 kev and where possible compared with other theoretical and experimental results.