Analysis of the α-particles emitted from thorium C and actinium C

Abstract

In a recent paper, an account has been given of the analysis of the long range α-particles emitted by radium C. Nine distinct groups of α-particles were detected varying in range between 7·8 and 11·6 cm. in air. Evidence was given that the emission of γ-rays from radium C is intimately connected with the occurrence of these groups of long range α-particles, and it was concluded that the γ-rays arise from the transition of an α-particle in an excited nucleus between two levels of different energies. This question has been discussed in more detail by Rutherford and Ellis, who have advanced a tentative theory to account for the relation between the energies of the γ-rays emitted from radium C. In the present paper we give the results of a corresponding analysis of the long range α-particles from thorium C and an analysis of the groups of α-particles emitted from actinium C. In these experiments the differential method of analysis was used, as in the experiments with radium C. In the present experiments, however, instead of recording the α-particles photographically on a moving film, we have mainly employed the automatic method of counting, using thyratrons in place of the oscillograph. This method, which has been developed by one of us (C. E. Wynn-Williams), has been fully discussed in a recent paper. Here it suffices merely to refer to one or two points of special interest in connection with the present research.