High spin states in 26Mg and 23Na populated by heavy ion reactions

Two experiments were used to produce high-spin states in sd-shell nuclei. Beams of 18O and 15N were extracted from the Oak Ridge National Laboratory EN tandem van de Graaff accelerator. Alpha particles from the 12C(18O,α)26Mg and 12C-(15N,α)23Na reactions were detected with a Borkowski-Kopp proportional counter at the focal plane of an Enge split-pole magnetic spectrograph. The differential cross sections extracted for many levels in the respective residual nuclei were averaged over several bombarding energies. These cross sections were analyzed in the framework of the Hauser-Feshbach formalism applicable to compound nuclear reactions. Both reactions are shown to be generally well predicted by the statistical model, though an apparent anomaly exists for certain states observed in the 12C(15N,α)23Na reaction. Several of the high-spin states are discussed in terms of the rotational model, and levels in 23Na are compared to high-spin state predictions from large basis shell model calculations