Angular distributions of alpha groups corresponding to elastic scattering and inelastic excitation of ${\mathrm{C}}^{12}$ to 4.43 MeV and of the proton group leading to the ground state of ${\mathrm{N}}^{15}$ have been measured at eight different energies between 20 and 23 MeV. The angular distributions show major changes over 400-keV energy intervals similar to those observed at higher and lower energies for the same scattering processes. The backward peaking in the ${\mathrm{C}}^{12}(\alpha , p){\mathrm{N}}^{15}$ reaction is not maintained over the energy region 22 to 25 MeV, as previously thought, but decreases again at energies slightly greater than 22 MeV.

• Received 27 March 1964

DOI:https://doi.org/10.1103/PhysRev.135.B660