Fine Structure in the ${\mathrm{C}}^{12}(\gamma , n){\mathrm{C}}^{11}$ and ${\mathrm{O}}^{16}(\gamma , n){\mathrm{O}}^{15}$ Activation Curves

A careful examination of the ${\mathrm{C}}^{12}(\gamma , n){\mathrm{C}}^{11}$ and ${\mathrm{O}}^{16}(\gamma , n){\mathrm{O}}^{15}$ reactions, resulting from irradiating samples with betatron bremsstrahlung, has revealed discontinuities in the yields as a function of peak bremsstrahlung energy. These discontinuities are interpreted to indicate the presence of strong photon absorption levels in the ${\mathrm{C}}^{12}$ and ${\mathrm{O}}^{16}$ nuclei. In ${\mathrm{C}}^{12}$ the discontinuities were found at 19.3, 19.8, 20.1, 20.5, 20.7, 21.1, 21.6, 22.4, and 22.8 Mev, and in ${\mathrm{O}}^{16}$ they were found at 15.9, 16.4, 16.7, 16.9, 17.1, 18.9, 19.3, 20.7, and 21.9 Mev. The experimental results are discussed in detail and are interpreted qualitatively.