The $\beta$ decay of ${\mathrm{Na}}^{20}$ proceeding to highly excited states of ${\mathrm{Ne}}^{20}$ has been studied by measuring the delayed $\alpha$ particles which are subsequently emitted. ${\mathrm{Na}}^{20}$ was produced by a ($p,\alpha n$) reaction on a natural magnesium target, in an external beam of 45-MeV protons from the UCLA cyclotron. A thin silicon detector and nanosecond electronics were used to suppress the large positron background usually present in this type of experiment. A method of measuring $Q_{\alpha }$ directly is discussed. $\alpha$ transitions from states in ${\mathrm{Ne}}^{20}$ at 7.43, 7.84, 8.74, 9.48, 10.28, 10.86, and 11.28 MeV have been observed and their intensities measured.

• Received 22 May 1967

DOI:https://doi.org/10.1103/PhysRev.163.1084