The simple theory of electron capture is outlined and three general methods for its detection are suggested. The first experimental evidence for the process (in activated titanium) is described. A rigorous experimental proof of the hypothesis is given for the case of ${\mathrm{Ga}}^{67}$. A summary of several isotopes whose properties are best explained on this hypothesis is appended. The properties of ${\mathrm{Ga}}^{67}$ are described in considerable detail, and include the first evidence for internal conversion in artificially radioactive atoms.

• Received 26 July 1938

DOI:https://doi.org/10.1103/PhysRev.54.486