The usefulness of the ${\mathrm{Be}}^9(\alpha , n)$ and the ${\mathrm{C}}^{13}(\alpha , n)$ reactions as sources of monoenergetic neutrons of variable energy was investigated. Measurements of the yield of the ${\mathrm{C}}^{13}(\alpha , n)$ reaction are presented. Total cross sections for elements of atomic number from 3 to 9 were measured for neutron energies between 4.4 and 5.6 Mev and between 7.6 and 8.6 Mev. The results give some information about energy levels in ${\mathrm{C}}^{13}$ and ${\mathrm{O}}^{17}$.

• Received 29 February 1956

DOI:https://doi.org/10.1103/PhysRev.102.1384