Differential Cross Sections in the Electron Impact Ionization of Atoms and Molecules

Angular distributions of ions produced in the electron impact ionization of a number of atoms and molecules have been measured for electron energies up to 300 eV. For ${\mathrm{He}}^{+}$ and ${\mathrm{Ar}}^{+}$ the ion distributions are found to mirror the "recoil" electron distributions of Ehrhardt and co-workers, thus confirming their explanation of their recoil peak. General trends in the angular distributions are summarized.