The excitation function at 90° c.m. has been measured between 7.5 and 27.5 MeV c.m. The prominent gross structure observed in ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$- ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ is not seen in the present case, and the absolute cross section falls to much lower values at high energies. The results of the comparison of the two systems are discussed in terms of angular momentum restrictions on configurations directly coupled to the elastic channel.

• Received 8 June 1970

DOI:https://doi.org/10.1103/PhysRevLett.25.457