Orientation and impact-parameter dependence of dissociative ionization of H2 by slow ion impact

We have used the cold target recoil ion momentum spectroscopy imaging technique to investigate dissociative ionization of H2 by 25 keV proton impact. A kinematically complete picture of the dissociative ionization dynamics for slow proton collision has been obtained. The results show a strong impactparameter dependence of the fragmentation process of H2. This clearly emerged in the energy distributions of the H + ions generated for different impact parameters. At large impact parameters the H + ions equally share the energy liberated in the collision whereas at small impact parameters, the energy sharing is quite asymmetric. We also observed a strong dependence of the electron emission on molecular alignment. The momentum distribution of the emitted electron generated for a fixed-in-space H2 molecule displays that the electrons are more likely to be emitted perpendicular to the molecular axis.