The mass of $^{22}$Mg

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