Study of the Low-Lying Excited States ofAl29. I.Si30(t, α)Al29Direct-Reaction Investigation

Abstract

The ${\mathrm{Si}}^{30}(t, \alpha ){\mathrm{Al}}^{29}$ reaction at a bombarding energy of 11.8 MeV has been used to investigate the states of ${\mathrm{Al}}^{29}$ up to 4.5-MeV excitation energy. From the deduced $l$ values of the picked-up protons, the spin parity of the 1.40-MeV state is confirmed as ${\mathrm{½}}^{+}$ and an assignment of $J^{\pi }={\frac{1}{2}}^{+}$ is made to the 3.43-MeV level. The states at 2.88, 3.07, 3.65, 3.68, and 4.23 MeV are assigned $J^{\pi }={(\frac{3}{2}, \frac{5}{2})}^{+}$. Tentative assignments of (${\frac{5}{2}}^{-}, {\frac{7}{2}}^{-}$) are made for both the 3.19-and 3.99-MeV states which are weakly excited in the experiment. Assuming that most of the proton pickup strength has been observed, the percentage occupation of protons in the ${\mathrm{Si}}^{30}$ ground state is deduced to be ${\left(1\mathrm{}{d}_{\frac{5}{2}}\right)}^2=82\%$, ${\left(2\mathrm{}{s}_{\frac{1}{2}}\right)}^2=7\%$, ${\left(1\mathrm{}{d}_{\frac{3}{2}}\right)}^2=7\%$, and ${\left(1\mathrm{}{f}_{\frac{7}{2}}\right)}^2\le 4\%$.