The Precise Measurement of Three Radium B Beta-Particle Energies

The $H_{\rho }$ of the three most intense Ra B $\beta$-particle lines have been measured by a precise magnetic spectrograph method and found to be 1406.0, 1671.1, and 1931.5 gauss cm. An explicit analysis has been made of the Cotton balance equations for $H$ in this experiment and on the basis of this a complete analysis was made of the maximum relative error to be expected in the accepted values of $H_{\rho }$. It is shown that the maximum relative error to be expected in the least $H_{\rho }$ is 1 part in 3000 and that within this possible error the greatest $H_{\rho }$ agrees with the value obtained by Scott. It is suggested that the accuracy of 1 part in 10,000 hoped for by Scott is rather too optimistic. The energies of these three $\beta$-particles are 1.512, 2.044, and 2.610 in units of ${10}^5$ electron volts. It is shown that the least of these cannot be expected to be any more accurate than 1 part in 1000. The conclusion is that expect for systematic errors which might have been present and undetected throughout this experiment and that of Scott, these experiments have established the values of these $H_{\rho }\text{'}\mathrm{s}$ to within 1 part in 3000.