On the stopping of fast particles and on the creation of positive electrons

The stopping power of matter for fast particles is at present believed to be due to three different processes: (1) the ionization; (2) the nuclear scattering; (3) the emission of radiation under the influence of the electric field of a nucleus. The first two processes have been treated in quantum mechanics by Bethe, Møller, and Bloch in a very satisfactory way. A provisional estimation of the order of magnitude to be expected in the third...