The origin of the γ -rays

In a recent paper, Rutherford, Ward and Lewis have described the results of their measurements on the long-rangeα -particles emitted by radium C. They were able to identify nine groups ofα -particles of different energies in addition to the group characterising the normal mode of disintegration. It was pointed out how the modern theories ofα -particle disintegration based on the wave mechanics make it possible to infer from these results the existence of a corresponding number of excited states of the radium C' nucleus. The excess of the energies of these stationary states over that of the ground state responsible for the normalα -particle are shown in Table I. It was shown that not only were these energy differences of the order of magnitude of the energies of theγ -rays emitted by radium C' immediately after the expulsion of theβ -particle from radium C, but that there were several instances of numerical agreement, which lent great weight to the suggestion that theγ -rays were due to transitions ofα -particles. We propose in this paper to consider this point of view in more detail and to examine some consequences that emerge.