Photofission of $^{238}$U at the energy of the Giant Dipole Resonance

Photofission of $^{238}U$ by bremsstrahlung photons is studied at four energies of the electron accelerator: 19.5, 29.1, 48.3, and 67.7 MeV. The yields of the fission fragments after the emission of prompt neutrons are obtained using the gamma - ray spectroscopic technique. The mass distributions of photofission are obtained at different upper energies of the bremsstrahlung spectrum. The ratio of the symmetric fission mode to the asymmetric is obtained from the mass distribution. The symmetric mode is shown to become 3-4 times greater than the asymmetric, as the excitation energy of the $^{238}U$ nucleus increases from 12 to 16 MeV