${}_{}{}^{21}{}_{}{}^{}\mathrm{F}\left({\beta }^{-}\right){}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ is re-examined. $\beta$ branches are observed as follows [${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}{E}_x$ (keV),% $\beta$ branch]: 0, 9.6(3.0); 351, 74.1(3.0); 1746, 16.1(1.0); 3736, 3.1(4)×${10}^{-3\mathrm{}}$; 3884, 4.0(4)×${10}^{-3\mathrm{}}$; 4525, 43(3)×${10}^{-3\mathrm{}}$; 4685, 77(5)×${10}^{-3\mathrm{}}$. The half-life was measured to be 4.158(20) s. Precision $\gamma$-ray measurements were made for the ${}_{}{}^{21}{}_{}{}^{}\mathrm{Ne}$ 351→0 and 1746→351 transitions and the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ 1634→0 transition. Results for the $\gamma$ energies are 350.725(8), 1395.131(17), and 1633.602(15) keV. $log\mathrm{ft}$ values are calculated. Comparisons of the present results are made to the shell-model calculations of Lanford and Wildenthal and to the analog ${\beta }^{+}$ decay of ${}_{}{}^{21}{}_{}{}^{}\mathrm{Mg}$ to ${}_{}{}^{21}{}_{}{}^{}\mathrm{Na}$. It is concluded that uncalculated Coulomb effects are a major block to the sensitivity of such comparisons.

RADIOACTIVITY ${}_{}{}^{21}{}_{}{}^{}\mathrm{F}$ [from ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}\mathrm{}(t,p)\mathrm{}$]; measured $I_{\gamma }$, $E_{\gamma }$, $T_{\frac{1}{2}}$; deduced $\beta$ and $\gamma$ branching, $log\mathrm{ft}$ values; compared with analog decay and theory.

• Received 4 September 1980

DOI:https://doi.org/10.1103/PhysRevC.23.1234