MASS DEPENDENCE OF FRAGMENT ANGULAR-DISTRIBUTIONS IN THE FISSION OF TH-232 AND U-236 INDUCED BY POLARIZED PHOTONS

Near-barrier fission of 232Th and U-236 induced by linearly polarized photons has been investigated. The experiments have been carried out a t the ''off-axis'' bremsstrahlung facility of the Giessen 65 MeV elect ron linac. Fragment angular, mass and energy distributions have been m easured simultaneously allowing the investigation of correlations betw een these fragment characteristics. A consistent assignment of the qua ntum numbers J(pi) and K for the fission channels involved in the fiss ion process is proposed. For the first time. the polar anisotropies an d azimuthal asymmetries of the fission fragment angular distributions W(theta, phi) have been investigated as a function of the fragment mas ses. The results are discussed in the framework of the double-humped f ission barrier concept and the so-called ''multi-exit fission channel' ' model. Additionally, angular distributions of heavy and light fissio n fragments from photofission of U-236 have been analyzed for a possib le asymmetry with respect to theta = 90-degrees.