A new method of positive ray analysis is described which lends itself particularly well to the study of the nature of the ions formed by single electron impact in gases, the efficiency of their production, and the measurement of their ionization potentials. The novel feature of the method is the use of the uniform magnetic field of a large solenoid so to concentrate a beam of electrons as to provide a linear source of positive ions. The ions are then pulled across the magnetic field and subjected to an $\frac{e}{m}$ analysis by a suitably designed analyser.

Some preliminary results are given for mercury vapor in which the ionization potentials of ${\mathrm{Hg}}^{2+}$, ${\mathrm{Hg}}^{3+}$, and ${\mathrm{Hg}}^{4+}$ are found at 30, 71, and 143 volts respectively.

• Received 8 June 1929

DOI:https://doi.org/10.1103/PhysRev.34.157