Tuning the internuclear distance in ionization of H ₂

The dependence of triply differential cross sections on the internuclear distance R is explored for ionization of molecular hydrogen by 200eV electrons for two distinct values R = 1.1 and 1.4au in comparison with helium as an isoelectronic system with a single nucleus (R = 0). A clear and systematic trend is observed with an increasing recoil-peak contribution with decreasing R. BBK-type model calculations indicate that the inclusion of the passive electron in the target wavefunction is the key ingredient for explaining the data rather than the two-centre character of the system.