In this paper we consider the behavior of electrons with energy very large compared to their proper energy in their passage through matter, and further treat the impacts suffered by a certain type of hypothetical elementary neutral particle whose existence was tentatively suggested by Pauli. In the introduction we outline the problem and the methods to be employed, and give a summary of the formulae which embody our results. In Section I we develop the method suggested by Møller for the relativistic treatment of impacts; in (a) we apply it to the impacts of two free electrons; in (b) we show how it is to be applied to those impacts of a fast electron in which little energy is transferred to the secondary; in (c) we develop the theory of the magnetic neutron, and apply Møller's method to the treatment of its impacts. In II we give the detailed calculation of the energy transfers from a fast electron to the electrons of the matter through which it is passing, and compute the range and ionizing power of the primary electron. In III we apply the theory of the neutron to compute the number and nature of its impacts.

• Received 18 July 1932

DOI:https://doi.org/10.1103/PhysRev.41.763