The γ-rays from actinium emanation and their origin

Abstract

As a result of recent experiments, evidence is accumulating that the pene­trating γ -rays from radioactive substances have their origin not in the movement of electrons but in the transitions of α -particles in an excited nucleus. Strong evidence in support of this view was obtained by Rutherford, Ward and Lewis from their analysis of the groups of long range α -particles from radium C', and a more detailed discussion of the results was given by Rutherford and Ellis. This problem of the origin of the γ -rays can be attacked in another direction from a consideration of the so-called fine structure shown by the groups of α -particles emitted by certain radioactive substances. In particular, Rosenblum found that the transformation of thorium C was accompanied by the appearance of five homogeneous groups of α -particles. In explanation of these results, Gamow suggested that γ -rays should be emitted as a result of such a complex transformation, the energies of the individual γ -rays corre­sponding to the differences of energies between the α -particles in the various groups. Unfortunately it is a difficult matter to give a decisive answer on this important question. In a recent paper, Ellis concludes that the experimental evidence is in support of Gamow’s theory, but on the other hand, Meitner as a result of her investigations, has expressed a contrary opinion. It is thus of much impor­tance to examine all methods of obtaining evidence on this question.