Experimental Test of Beta-Ray Theory for the Positron Emitters ${\mathrm{Na}}^{22}$, ${\mathrm{V}}^{48}$, ${\mathrm{Mn}}^{52}$, ${\mathrm{Co}}^{58}$

The positron branching ratio $\frac{{\lambda }_{+}}{({\lambda }_c+{\lambda }_{+})}$ has been measured by a coincidence counting method for four isotopes in which radioactive decay involves competition between positron beta-rays and orbital electron capture. The results are ${}_{11}{}^{}{}_{}{}^{}\mathrm{Na}_{}^{22}{}_{}{}^{}$: 1.00±0.05, ${}_{23}{}^{}{}_{}{}^{}\mathrm{V}_{}^{48}{}_{}{}^{}$: 0.58±0.04, ${}_{25}{}^{}{}_{}{}^{}\mathrm{Mn}_{}^{52}{}_{}{}^{}$: 0.35±0.02, ${}_{27}{}^{}{}_{}{}^{}\mathrm{Co}_{}^{58}{}_{}{}^{}$: 0.145±0.005. It is shown that these values, as well as the observed shapes of the beta-ray spectra, and the observed lifetimes are in agreement with predictions of the beta-ray theory for nuclear angular momentum changes $\Delta I=0\mathrm{}$ or $\Delta I=\pm 1$. The type of interaction remains uncertain, as does the parity change, except that the scalar interaction gives consistent results if one assumes the parity change in every case except ${\mathrm{Mn}}^{52}$.