The Capture and Loss of Electrons by Helium Ions in Helium

Mean free paths for capture ($L_1$) and loss ($L_0$) of electrons by helium ions in helium have been measured by a method whose chief novelty is the use of an ion source which gives quite strictly homogeneous velocities. In the range of velocities 0.6 × ${10}^8$ cm/sec. to 1.0 × ${10}^8$ cm/sec. $L_0$, reduced to 760 mm, is found to decrease from 21.5 × ${10}^{-4\mathrm{}}$ cm to 8.6 × ${10}^{-4\mathrm{}}$ cm and $L_1$ is practically constant at 1.2 × ${10}^{-4\mathrm{}}$ cm. These results are compared to similar measurements by other observers, particularly with regard to the manner of dependence on velocity. The relation of the results to available information on ionization and energy loss is discussed.