A recent experiment located the lowest 2${}^{+}$ state in ${}^{20}$Mg and discovered that the corresponding 2${}^{+}$, $T$ $=$ 2 state in ${}^{20}$F does not fit expectations of the isobaric multiplet mass equation without a $d$ term. We have calculated the energies of the ground and 2${}^{+}$ states in ${}^{20}$Mg and the 2${}^{+}$ in ${}^{20}$F in a potential model, using shell-model spectroscopic factors. We conclude that this important ${}^{20}$F state has likely never been observed, and suggest a reaction to find it.

• Received 19 February 2012

DOI:https://doi.org/10.1103/PhysRevC.85.054304