The Mass ofMg22

Mass measurements with a relative precision of better than $1.5\times {10}^{-8}$ were performed on ${}^{22}\mathrm{M}\mathrm{g}$ and its reaction partners ${}^{21}\mathrm{N}\mathrm{a}$ and ${}^{22}\mathrm{N}\mathrm{a}$ with the ISOLTRAP Penning trap mass spectrometer at CERN, yielding the mass excesses $D({}^{22}\mathrm{M}\mathrm{g})=-399.92(27)\mathrm{k}\mathrm{e}\mathrm{V}$, $D({}^{21}\mathrm{N}\mathrm{a})=-2184.71(21)\mathrm{k}\mathrm{e}\mathrm{V}$, and $D({}^{22}\mathrm{N}\mathrm{a})=-5181.56(16)\mathrm{k}\mathrm{e}\mathrm{V}$. The importance of these results is twofold. First, a comparative half-life ($Ft$ value) has been obtained for the superallowed $\beta$ decay of ${}^{22}\mathrm{M}\mathrm{g}$ to further test the conserved-vector-current hypothesis. Second, the resonance energy for the ${}^{21}\mathrm{N}\mathrm{a}$ proton capture reaction has been independently determined, allowing direct comparisons of observable $\gamma$ radiation in nova explosions with the yield expected from models.