Spin-parity combinations in 28Al

The tensor analyzing powers T₂₀ and the cross sections for the reaction ${}^{30}\text{Si}\text{(}\text{d}\text{, α)}{}^{28}\text{Al}$ to levels in ²⁸Al with excitation energies up to 5.3 MeV have been measured at θ_lab = 175° for bombarding energies from 8.0 to 12.0 MeV in steps of 0.5 MeV. Comparison of the measured T₂₀ values with theoretical predictions has led to assignments of natural or unnatural parity to some forty levels in ²⁸Al. In a number of cases unique spin-parity assignments could be deduced by combining the present information with published spectroscopic data. A (probable) assignment of J^π = 0⁺ could be made to three levels in ²⁸Al on the basis of a very low observed cross section. No states with J^π = 0^? have been observed for E_x < 5.3 MeV. The distribution of T₂₀ values measured in cases where the final state has unnatural parity has been found to be in agreement with the prediction of the statistical theory for nuclear reactions. The spectroscopic information is compared with existing shell-model calculations.