Fragment angular distributions from fission of238U,209Bi and197Au by 140-MeV4He Ions

Abstract

Abstract. The fission fragment angular distributions from reactions of 140-MeV 4He ions with 23sU, 2~ and 197Au have been studied. From the anisotropies in the angular distributions, values for Jeff, the effective moment of inertia at the fission saddle point, have been estimated and compared with results obtained at lower bombarding energies. The derivation of ~ff values has included corrections for the effects of incomplete fusion mechanisms on the orbital angular momentum distribution of the fissioning nuclei and for neutron evaporation prior to fission. The results are also compared with heavy-ion-induced fission data for systems of similar fissility. Also, examination of the forward-backward symmetry of the 23su angular distribution substantiates other results which show that the fraction of fission reactions which follow complete fusion of the target and projectile is less than 0.5 for 140-MeV 4He-ion bombardment of 23su.Nuclear Reactions, Fission 23Su(o~,f), 2~197Au(o~,f), E= 140 MeV; measured cr(0); deduced effective moment of inertia.

Nuclear Physics Laboratory 1980 annual report

“…If in the analysis of these light ion data the 2-wave distribution is modified to account for incomplete fusion, then Clark et a1. 9 has found for uranium-like nuclei a linear relationship between Kft and E}/ 2 where Ef is the excitation energy of the fissioning nucleus minus its saddle point energy. Also, in our study of the Kr + Bi fission fragment data 2 • 3 we found a linear relationship between K6 and E{/ 2 for the less fissile Ac-like nuclei.…”