Study of Levels inMg23

Abstract

Levels in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$ with excitation energies up to 6.8 MeV have been investigated by magnetic analysis of the $\alpha$ particles from the reaction ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}({}_{}{}^3{}_{}{}^{}\mathrm{He}, \alpha ){}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$ at bombarding energies between 6 and 12 MeV. Between 4.4- and 6.8-MeV excitation energy, 16 new levels were found in ${}_{}{}^{23}{}_{}{}^{}\mathrm{Mg}$. Angular distributions of the emitted $\alpha$ particles were measured and from distorted-wave Born-approximation analysis $l$ values for the picked up neutrons were obtained. The particle-$\gamma$ angular-correlation method of Litherland and Ferguson was used to obtain additional information on the spin assignments of the levels as well as branching and mixing ratios of the $\gamma$-ray transitions. The following spin and parity assignments have been established for the indicated levels: 0.451 MeV ${\frac{5}{2}}^{+}$, 2.048 MeV $\frac{7}{2}$ ($\frac{3}{2}$), 2.356 MeV ${\mathrm{½}}^{+}$, 2.768 MeV ${(\frac{1}{2}, \frac{3}{2})}^{-}$, 2.904 MeV ${(\frac{3}{2}, \frac{5}{2})}^{+}$, 3.792 MeV ${\frac{3}{2}}^{-}$, 4.353 MeV ${\mathrm{½}}^{+}$, 5.289 MeV ${(\frac{3}{2}, \frac{5}{2})}^{+}$, and 5.992 MeV ${(\frac{1}{2}, \frac{3}{2})}^{-}$. The experimental results are compared with those obtained for ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ and the predictions of the collective model.