Investigatkion of the Levels inNa23below 3 MeV by theMg26(p,αγ)Na23Reaction

Abstract

The particle-gamma angular correlation method of Litherland and Ferguson was used to gain information on the decay modes and spin assignments of the levels in ${\mathrm{Na}}^{23}$ below 3 MeV as well as the mixing ratios of the transitions from these levels. The ${\mathrm{Mg}}^{26}(p,\alpha ){\mathrm{Na}}^{23}$ reaction was used at proton energies between 9.3 and 10.5 MeV. The spin of the first excited state was verified as $\frac{5}{2}$. Rigorous limitations are given for the spins of the other five levels, the most probable assignment being 2.08 MeV (${\frac{7}{2}}^{\mathrm{}(+)\mathrm{}}$), 2.39(${\mathrm{½}}^{\mathrm{}(+)\mathrm{}}$, 2.64(½), 2.71 ($\frac{9}{2}$), 2.98 ($\frac{3}{2}$). The results are discussed in terms of the Nilsson model for the $N or Z=11\mathrm{}$ nuclei. In particular the phases of the mixing ratios of the transitions from the first two excited states of these nuclei are compared. The problem of the comparison of the signs of the experimentally determined mixing ratios quoted by different authors is also treated.