Sargent Diagram and Comparative Half-Lives for Electron Capture Transitions

Earlier studies by Thompson and Feather have been extended to lighter nuclei, wherever the half-life, branching ratios, and transition energy $W$ are known, and a Sargent diagram constructed for 87 electron capture transitions; $W$, defined as the energy of the neutrino emitted during capture, must be deduced indirectly, from atomic mass differences, positron spectra, or inner bremsstrahlung. Known allowed transitions fall considerably below the line proposed by Feather, but the scatter of the points does not permit differentiation of Sargent curves for different degrees of forbiddenness. Comparative half-lives have been calculated for these capture transitions, and are tabulated and compared with $\mathrm{ft}$ values for beta emitters. The distribution of $\mathrm{ft}$ values are similar, and agreement is evident between most $\mathrm{ft}$ values for electron capture and positron emission in the same transformation.