The passage of neutrons through matter

Abstract

The interactions between neutrons and matter which have been chiefly investigated hitherto are of the types discovered by Fermi in which the neutron is either scattered elastically or absorbed with or without the emission of a proton or α-particle. The experiments to be described were started with the object of finding out whether any other type of interaction exists; some preliminary experiments by Fermi and others and Lea suggest that there are inelastic collisions in which the energy lost by the neutrons appears ultimately as a photon, and the results of our experiments can be interpreted in terms of this simple hypothesis. Since neutrons can at present only be classified on an experimental basis, it is very convenient to use a nomenclature based upon Fermi's theory, which attributes the observed difference in properties entirely to a difference in velocity. In this way one can avoid a continual and very cumbersome reference to the experimental arrangement, without lack of precision.