The angular distributions of the $\alpha$-particle groups from the ${\mathrm{C}}^{13}({\mathrm{He}}^3, \alpha ){\mathrm{C}}^{12}$ reaction which leave the ${\mathrm{C}}^{12}$ nuclei in the ground and first excited states have been measured at a bombarding energy of 4.5 Mev. The angular distributions have been fitted with Legendre polynomial expansions. In order to fit the data within the experimental uncertainties it was necessary to include polynomials up to the eighth degree in these expansions. It appears unlikely that the angular distributions can be accounted for on the basis of compound-nucleus type of reaction. Although the usual concept of a pickup type reaction also encounters difficulties in attempting to account for this reaction, theoretical calculations based on this type of process have been compared with the experimental results. Other possible mechanisms by which this reaction may take place are suggested.

• Received 31 December 1956

DOI:https://doi.org/10.1103/PhysRev.106.102