Fine structure previously observed in the ${\beta }^{+}$ activation curves of ${\mathrm{C}}^{11}$ and ${\mathrm{O}}^{15}$ resulting from the betatron induced reactions ${\mathrm{C}}^{12}(\gamma , n){\mathrm{C}}^{11}$ and ${\mathrm{O}}^{16}(\gamma , n){\mathrm{O}}^{15}$ is shown to be present in the neutron yield curves from these reactions by detecting the emitted neutrons. The position of this fine structure as a function of betatron operating energy is the same in both cases to within experimental accuracy. The ${\mathrm{Li}}^7(\gamma , n){\mathrm{Li}}^6$ and ${\mathrm{F}}^{19}(\gamma , n){\mathrm{F}}^{18}$ were examined and discontinuities in the neutron yield curves were found at 9.6, 10.8, 12.4, 14.0, and 17.5 Mev for the first reaction and 11.0, 11.5, 11.9, and 15.3 for the second.

• Received 7 April 1954

DOI:https://doi.org/10.1103/PhysRev.95.471