Excitation functions for ($p, 2p$), ($p, \alpha$), and ($p, 2\alpha$) reactions on ${\mathrm{Mg}}^{25}$ were measured with the internal 22-Mev proton beam of the 86-inch cyclotron. The results are compared with the excitation functions obtained for the reactions produced by 29-Mev nitrogen ions on carbon in the 63-inch cyclotron. Both sets of reactions may proceed via the same compound nucleus, ${\mathrm{Al}}^{26}$. After corrections for the barrier penetrations of the incident particles, the (N, $2p$) and ($p, 2p$) results are quite comparable. The corrected (N, $\alpha$) and (N, $2\alpha$) cross sections are larger than those for the corresponding proton-induced reactions by factors of about two and four respectively, indicating that processes other than conventional compound nucleus formation are involved in these nitrogen-induced reactions. The shape of the excitation functions for the nitrogen-induced reactions indicates that the protons and alpha particles are emitted from nearly spherical nuclei with charge equal to that of the compound nucleus; direct interactions such as stripping are thus excluded.

• Received 19 August 1954

DOI:https://doi.org/10.1103/PhysRev.96.1617