Atomic Electron Velocities in Hydrogen

When conditions are favorable to single scattering of fast electrons, those scattered through a suitable angle by gases of low atomic number fall into two distinct classes, (1) those scattered elastically by the nuclei and (2) those scattered inelastically by the atomic electrons. The inelastically scattered electrons have a distribution of energies about the most probable value, which is $V=V_0{cos}^2\theta$, where $V_0$ and $V$ are the energies of the incident electron before and after collision with an atomic electron, and $\theta$ is the angle of deflection. The distribution of energies among the inelastically scattered electrons is determined by the distribution of energies among the atomic electrons in such a way that the curve representing the distribution of energies among the scattered electrons, above or below the most probable value, is identical in shape with the distribution of component velocities among the atomic electrons. A beam of electrons with energies between 1737 and 4040 volts was directed into hydrogen at low pressure and the distribution of energies among those electrons which had been scattered at 34.2° measured. From this the distribution of component velocities among the atomic electrons follows immediately. The experimental curve is wider than the theoretical curve computed by Hicks by about 11 percent at the "half-width." In view of the exact agreement obtained previously with the same method in the case of helium, it is suggested that the assumptions underlying the theoretical calculation for the hydrogen molecule may have to be revised.