Measurement of alignment dependence in single ionization of hydrogen molecules by fast protons*

Relative cross sections for the 4 MeV H$^{+}$ + D$_{2}$ ($^{1}\Sigma _{g}^{+})^{ }\to $ D$_{2}^{+}$(1$s\sigma )$ + e$^{-}$ process are measured as a function of the molecular alignment during the interaction. The angle between the molecular axis and the projectile is obtained by using a momentum imagining technique and isolating the events in which the D$_{2}^{+}$(1$s\sigma )$ ions are excited to the vibrational continuum of the electronic ground state and subsequently dissociate. While several theoretical models suggest different angular distributions, and anisotropic distributions have been observed for double ionization of D$_{2}$, our preliminary results do not show significant anisotropies.