Decays ofNa26andNa27

Abstract

$^{26}\mathrm{Na}$ and $^{27}\mathrm{Na}$ were produced in the $^{10}\mathrm{B}(^{18}\mathrm{O},2p)^{26}\mathrm{Na}$ and $^{11}\mathrm{B}(^{18}\mathrm{O},2p)^{27}\mathrm{Na}$ reactions by bombarding pellets of boron with 42-MeV $^{18}\mathrm{O}$ ions. $^{26}\mathrm{Na}$ was also studied using the $^{18}\mathrm{O}(^{13}\mathrm{C},p\ensuremath{\alpha})^{26}\mathrm{Na}$ reaction at a $^{13}\mathrm{C}$ beam energy of 35 MeV. After transfer of the target in a rabbit the $\ensuremath{\beta}$ and $\ensuremath{\gamma}$ rays were measured with NE102 and Ge(Li) detectors. $^{26}\mathrm{Na}$ decays with ${T}_{\frac{1}{2}}=1.087\ifmmode\pm\else\textpm\fi{}0.012$ sec and emits 10 $\ensuremath{\gamma}$ rays involving 7 excited states of $^{26}\mathrm{Mg}$. From the end-point energy of $\ensuremath{\beta}$ rays in coincidence with 1809-keV $\ensuremath{\gamma}$ rays the mass excess of $^{26}\mathrm{Na}$ is found to be -7004 \ifmmode\pm\else\textpm\fi{} 200 keV in agreement with the more accurate data of reaction $Q$ values. $^{27}\mathrm{Na}$ decays with ${T}_{\frac{1}{2}}=280\ifmmode\pm\else\textpm\fi{}20$ msec in agreement with a previous measurement. $\ensuremath{\gamma}$ rays of 984.77 \ifmmode\pm\else\textpm\fi{} 0.20 and 1698.5 \ifmmode\pm\else\textpm\fi{} 0.5 keV are emitted with relative intensities of 86.0 \ifmmode\pm\else\textpm\fi{} 2.9 and 14.0 \ifmmode\pm\else\textpm\fi{} 2.3, respectively. The spin of $^{27}\mathrm{Na}$ is established as ${J}^{\ensuremath{\pi}}={\frac{3}{2}}^{+} or {\frac{5}{2}}^{+}$ from these data. From the end-point energy of $^{27}\mathrm{Na}$ $\ensuremath{\beta}$ rays in coincidence with 985-keV $\ensuremath{\gamma}$ rays, compared with $^{26}\mathrm{Na}$ $\ensuremath{\beta}$ rays, the mass excess of $^{27}\mathrm{Na}$ is -5650 \ifmmode\pm\else\textpm\fi{} 180 keV based on the $^{26}\mathrm{Na}$ mass. This result is in fair agreement with a recent direct determination of the $^{27}\mathrm{Na}$ mass.