Masses of the unbound nucleiNe16,F15, andO12

The (${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{He}$) and (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$) reactions have been employed at detection angles near 8° on gas targets of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ to produce and measure the masses of the nuclei ${}_{}{}^{16}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{F}$, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{O}$. The (${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{He}$) reactions were performed at an incident energy of 117 MeV and the (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$) reaction at 88 and 75 MeV. The mass excesses of ${}_{}{}^{16}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{F}$, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{O}$ were determined to be 23.92±0.08, 16.67±0.18, and 32.10±0.12 MeV, respectively. Estimated ground state decay widths were ${\Gamma }_{\mathrm{c}.\mathrm{m}.\mathrm{}}=0.2\mathrm{}\pm 0.1, 0.8\pm 0.3, \mathrm{and} 0.40\pm 0.25$ MeV, for ${}_{}{}^{16}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{15}{}_{}{}^{}\mathrm{F}$, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{O}$, respectively. A $d$ coefficient of 8±5 keV is indicated for the isobaric multiplet mass equation description of the mass 16 multiplet. Consideration of the possible decay mechanisms of ${}_{}{}^{16}{}_{}{}^{}\mathrm{Ne}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{O}$ indicates that both nuclei probably have an appreciable diproton decay width.