We complete a previous description of classical ionization in ${\mathrm{He}}^{2+}+\mathrm{H}$ collisions, extending the energy range of the illustrations and using as initial conditions either a microcanonical distribution or a hydrogenic one that produces better cross sections near threshold. We call those ionizing electrons that are bound in a frame where the nuclear motion is suppressed molecular-type electrons. We illustrate the evolution of these electrons in phase space, and show that it may properly be called saddle-point ionization at low nuclear velocities, while they give rise at high energies to the standard direct ionization process.

• Received 9 June 1997

DOI:https://doi.org/10.1103/PhysRevA.57.1809