[en] The β-ν correlation coefficient, a_βν, is measured in ²¹Na by detecting the time of flight of the recoil nucleus detected in coincidence with the atomic electrons shaken off in β decay. The sample of ²¹Na is confined in a magneto-optic trap. High detection efficiency allows low trap density, which suppresses the photoassociation of molecular sodium, which can cause a large systematic error. Suppressing the fraction of trapped atoms in the excited state by using a dark trap also reduces the photoassociation process, and data taken with this technique are consistent. The main remaining systematic uncertainties come from the measurement of the position and size of the atom trap and the subtraction of background. We find a_βν=0.5502(60), in agreement with the Standard Model prediction of a_βν=0.553(2), and disagreeing with a previous measurement, which was susceptible to an error introduced by the presence of molecular sodium

[en] The charge-state distribution following the β⁺ decay of²¹Na has been measured, showing a larger than expected fraction of the daughter ²¹Ne in positive charge states. No dependence on either the β⁺ or recoil nucleus energy is observed. The data are compared to a simple model based on the sudden approximation. Calculations suggest that a small but important contribution from recoil ionization has significant consequences for precision β decay correlation experiments detecting recoil ions

[en] We have measured the half-life of ¹⁴O, a superallowed (0⁺→0⁺) β decay isotope. The ¹⁴O was produced by the ¹²C(³He,n)¹⁴O reaction using a carbon aerogel target. A low-energy ion beam of ¹⁴O was mass separated and implanted in a thin beryllium foil. The beta particles were counted with plastic scintillator detectors. We find t_1/2=70.696±0.052 s. This result is 1.5σ higher than an average value from six earlier experiments, but agrees more closely with the most recent previous measurement