High-precision half-life measurements for the superallowed Fermiβ+emitterNe18

The half-life of the superallowed Fermi ${\ensuremath{\beta}}^{+}$ emitter $^{18}\mathrm{Ne}$ has been determined via two high-precision $\ensuremath{\beta}$ counting experiments at TRIUMF's Isotope Separator and Accelerator facility. Using two different $4\ensuremath{\pi}$ continuous-flow gas-proportional counters, two independent measurements were made, yielding a weighted average of ${T}_{1/2}=1.{66400}_{\ensuremath{-}0.00048}^{+0.00057}$ s, which is consistent with but approximately 2 times more precise than a previous high-precision measurement based on $\ensuremath{\gamma}$-ray counting. The present work achieves $\ifmmode\pm\else\textpm\fi{}0.034%$ precision for the $^{18}\mathrm{Ne}$ half-life and will enable the inclusion of $^{18}\mathrm{Ne}$ among the set of precisely measured superallowed Fermi $\ensuremath{\beta}$-decay $ft$ values once improved measurements are made for its $Q$ value and superallowed branching ratio. As a test of systematic uncertainties, the half-life of $^{23}\mathrm{Ne}$ was measured and the world average has been improved, by a factor of 1.7, to $37.148\ifmmode\pm\else\textpm\fi{}0.032$ s.