Beta decay ofNa27−32and their descendants

The $\gamma$ activities from the $\beta$ decay of Na isotopes up to ${}_{}{}^{32}{}_{}{}^{}\mathrm{Na}$, which are formed in high-energy fragmentation and analyzed through mass spectrometry techniques, are observed, as well as those from their Mg or Al descendants. Their intensities are measured, in most cases, in absolute value. The radioactive half-lives of ${}_{}{}^{29}{}_{}{}^{}\mathrm{Mg}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{31}{}_{}{}^{}\mathrm{Mg}$ are determined. Delayed-neutron branching ratios $P_n$ are measured for ${}_{}{}^{29}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{30}{}_{}{}^{}\mathrm{Na}$, and ${}_{}{}^{32}{}_{}{}^{}\mathrm{Na}$. In some cases, partial branching ratios to excited states of the daughter nucleus are also measured. The most prominent $\gamma$ ray in the $\beta$ decay of even Na isotopes is assigned to $2^{+}$ →$0^{+}$ transition in the daughter Mg isotopes. The position of the first excited $2^{+}$ level is therefore deduced for ${}_{}{}^{30}{}_{}{}^{}\mathrm{Mg}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{Mg}$. For ${}_{}{}^{32}{}_{}{}^{}\mathrm{Mg}$, the excitation energy drops markedly. It is taken as an indication of a stronger deformation for that isotope.