Mass dependence of azimuthal asymmetry in the fission of 232Th and 233,235,236,238U by polarized photons

Fission of the even-even nuclei 232Th, 236,238U and even-odd nuclei 233,235U by linearly polarized photons has been studied at excitation energies in the region of a giant dipole resonance. The performed investigations unambiguously showed the existence of the fragment mass dependence of the cross section azimuthal asymmetry in the photofission of 236U and 238U. In addition, the obtained results provided the first evidence for the possible difference between the asymmetry values in asymmetric and symmetric mass distribution regions in the case of 236U. The measured cross section azimuthal asymmetry of the fission of 232Th does not show any fragment mass dependence. In the even-odd nuclei 233U and 235U the difference between the far-asymmetric and other mass distribution regions was also observed but with the statistical uncertainty not small enough for definitive conclusion.