Light-mass yields and fine structure of mass distributions in ${}^{232}\mathrm{Th}$ photofission

Fission-fragment mass distributions in the ${}^{232}\mathrm{Th}(\gamma ,f)$ reaction have been measured from the cumulative yields of radionuclides following activation at bremsstrahlung endpoint energies $E_e=7.5,$ 12.0, and 24.0 MeV. The yields of the light nuclei ${}^{24}\mathrm{Na}$ and ${}^{28}\mathrm{Mg}$ were detected following activation at $E_e=16.5\mathrm{}$ and 24.0 MeV. Energy dependences of the symmetric mode and light nuclide yields are discussed. Fine-structure manifestations near asymmetric and symmetric masses were observed.