Angle and Energy Distribution of Electrons Scattered by Helium, Argon and Hydrogen

The distribution of electrons rebounding at definite angles from gaseous molecules was investigated. An electrostatic re-focussing arrangement was used to analyse the energies of the electrons. In helium, it was possible to identify the following energy losses at several angles, 21.12, 22.97, and 23.62 volts for a primary electron beam of 50 volts, but not the 19.77 and 20.55 volt losses.The number of electrons, rebounding without loss of energy, was measured for different angles of rebound (7^∘{} to 60^∘{}) from argon, helium, and molecular hydrogen molecules, and for various energies (50 to 150 volts). A scattering curve was also obtained in helium for 100 volt electrons that had lost 21.12 volts energy. In almost all cases, the number scattered decreased rapidly as the angle increased. The higher the energy of the electrons, the more rapidly did the number fall off with increasing angle. The steepness of the curves increases as we go from argon to helium to hydrogen for the slower electrons. For the faster electrons their curves are practically superposable.The results were compared with those of other observers and with the theoretical predictions of Mott, Mitchell and Sommerfeld.