Average Energy of Beta-Rays Emitted by Radioactive Isotopes

For those radio elements whose beta-ray spectra have been adequately investigated, the average kinetic energy ${\overline{E}}_{\beta }$ is computed by graphical methods. ${\overline{E}}_{\beta }$ is calculated also as a function of the atomic number $Z$ and the spectral limit $E_o$ by means of Fermi's theory for allowed transitions, and compared to these experimental results. It is found that only the well-known experimental values of ${\overline{E}}_{\beta }$ for the forbidden spectrum of RaE deviates very markedly from the calculated one.