| Popis: |
The pion double-charge exchange reaction (${\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}}$) has been used to measure the ground-state masses of $^{12}\mathrm{O}$, $^{16}\mathrm{Ne}$, $^{24}\mathrm{Si}$, and $^{32}\mathrm{Ar}$. The mass excesses were found to be 32.059(48), 24.051(45), 10.682(52), and - 2.181(50) MeV, respectively. These are the first reported measurements of the masses of $^{24}\mathrm{Si}$ and $^{32}\mathrm{Ar}$ and the values for $^{12}\mathrm{O}$ and $^{16}\mathrm{Ne}$ are improved over previous results. Good agreement with the isobaric multiplet mass equation $M=a+b{T}_{z}+c{{T}_{z}}^{2}$ is obtained for the known members of all four quintets.NUCLEAR REACTIONS Pion double-charge exchange, $^{9}\mathrm{Be}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})^{9}\mathrm{C}$, $^{12}\mathrm{C}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})^{12}\mathrm{O}$, $^{13}\mathrm{C}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})^{13}\mathrm{O}$, $^{16}\mathrm{O}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})^{16}\mathrm{Ne}$, $^{24}\mathrm{Mg}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})^{24}\mathrm{Si}$, $^{32}\mathrm{S}({\ensuremath{\pi}}^{+}, {\ensuremath{\pi}}^{\ensuremath{-}})^{32}\mathrm{Ar}$, $E=180$ MeV, measured $Q$ and $\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}}$ (5\ifmmode^\circ\else\textdegree\fi{}). |
