The cross sections for the double ionization, ionization plus excitation, and double excitation of ${\mathrm{H}}_2$ by protons and electrons have been measured as a function of the angle between the internuclear axis of the target and the projectile-beam direction. Measurements are reported for angles ranging from 18° to 90° and projectile-beam energies of 0.75, 1.0, and 2.0 MeV/amu. Simple model calculations predict a different angular dependence depending on whether the final configuration of a particular reaction channel is or is not dipole allowed. Comparison is made between prediction and measurement. For both electron and proton projectiles, the sum of the yield in all channels follows the form corresponding to a dipole-allowed final state. Some individual channels do not.

• Received 17 June 1992

DOI:https://doi.org/10.1103/PhysRevA.46.6970