Angular distribution measurements have been carried out on the protons corresponding to the ground state transition in the ${\mathrm{B}}^{10}(\alpha , p){\mathrm{C}}^{13}$ reaction at bombarding energies of 8.1, 7.0, and 4.9 Mev, on the protons corresponding to the ground state and first-excited state transitions in the ${\mathrm{Al}}^{27}(\alpha , p){\mathrm{Si}}^{30}$ reaction at bombarding energies of 8.1 and 7.1 Mev, and on the protons corresponding to the ground state transition in the ${\mathrm{P}}^{31}(\alpha , p){\mathrm{S}}^{34}$ reaction at bombarding energies of 8.1 and 7.0 Mev. According to rather qualitative criteria concerning the changes in the shapes of the distributions with bombarding energy, the Al results appear to be interpretable in terms of a compound nucleus process, while the B and P results indicate the possibility of a contribution from a direct interaction process. Some discussion is given concerning the possibility of applying a direct interaction process like that of Austern, Butler, and McManus to such alpha-particle-induced reactions.

• Received 16 November 1956

DOI:https://doi.org/10.1103/PhysRev.105.1556