Single ionization of hydrogen molecules by fast protons as a function of the molecular alignment

Relative cross sections for the $4\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ ${\mathrm{H}}^{+}+{\mathrm{D}}_{2}$ $(^{1}\ensuremath{\Sigma}_{g}^{+})\ensuremath{\rightarrow}{\mathrm{H}}^{+}+{\mathrm{D}}_{2}^{+}(1s\ensuremath{\sigma})+{e}^{\ensuremath{-}}$ ionization process were measured as a function of the molecular alignment during the interaction. The angle between the molecular axis and the projectile was obtained by using a momentum imagining technique and isolating the events in which the ${\mathrm{D}}_{2}^{+}(1\mathrm{s}\ensuremath{\sigma})$ ions are excited to the vibrational continuum and subsequently dissociate. While anisotropic cross sections have been observed in the past for a number of collision processes involving both target electrons, the one electron process investigated here is isotropic within our experimental uncertainties.