Isospin Purity and Delayed-Proton Decay:Ne17andAr33

$\beta$-delayed proton and $\gamma$-ray measurements have been used to study the decay of ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{33}{}_{}{}^{}\mathrm{Ar}$. Their half-lives have been measured as 109.0 ± 1.0 and 173.0 ± 2.0 msec, respectively, and absolute $\mathrm{ft}$ values have been determined for their $\beta$-decay branches. Precise level energies have been measured in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ and ${}_{}{}^{33}{}_{}{}^{}\mathrm{Cl}$, and an earlier discrepancy concerning energies in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ has been resolved. The $log\mathrm{ft}$ value for the superallowed decay branch of ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$ has been measured to be ${3.29}_{-0.07\mathrm{}}^{+0.04\mathrm{}}$, which indicates an isospin purity of ≥95% for the lowest $T=\frac{3}{2}$ state in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$. In addition, the antianalog configuration is located in ${}_{}{}^{17}{}_{}{}^{}\mathrm{F}$ and is shown to be the most probable source of the small isospin mixing present in the analog state in that nucleus. The $log\mathrm{ft}$ value measured for the superallowed decay branch from ${}_{}{}^{33}{}_{}{}^{}\mathrm{Ar}$ was 3.34 ± 0.05, a value which suggests an impurity of ∼10% in the lowest $T=\frac{3}{2}$ state in ${}_{}{}^{33}{}_{}{}^{}\mathrm{Cl}$. There is circumstantial evidence that this mixing occurs with four $T=\frac{1}{2}$ states which lie within 350 keV of the analog state.