The relative velocities of the alpha-particles from thorium X and its products and from radium C'

Abstract

During the last few years determinations of the velocities of emission of α-particles have been made by Briggs, Laurence and by Rosenblum and his co-workers. The discrepancies between the values obtained for the relative velocities of thorium C, thorium C' and radium C', which are collected in this paper in Table VIII, indicate the uncertainty that existed as to the correct values of α-ray velocities. Much of this uncertainty has been removed by the recent determination by Rosenblum and Dupouy of the absolute velocities of the α-particles of radium C' and polonium, and the velocities relative to them of the α-particles of thorium C a , thorium C', actinium C a , actinium C a 1 and radium A. These measurements were made after a new exploration of the field of the large electro-magnet of the Academy of Sciences which enabled the accuracy of measurement to be increased to 1 or 2 in 2000 and appears to have removed a systematic source of error in the earlier velocity determinations made with this magnet in the course of the investigation of the fine structure of α-ray spectra.