High-precision half-life measurements for the superallowed Fermi β+ emitter 18Ne.

The half-life of the superallowed Fermi β+ emitter 18Ne has been determined via two high-precision β counting experiments at TRIUMF's Isotope Separator and Accelerator facility. Using two different 4π continuous-flow gas-proportional counters, two independent measurements were made, yielding a weighted average of T1/2=1.66400+0.00057-0.00048 s, which is consistent with but approximately 2 times more precise than a previous high-precision measurement based on γ-ray counting. The present work achieves ±0.034% precision for the 18Ne half-life and will enable the inclusion of 18Ne among the set of precisely measured superallowed Fermi β-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 23Ne was measured and the world average has been improved, by a factor of 1.7, to 37.148±0.032 s. [ABSTRACT FROM AUTHOR]