Evidence for different fission fragment mass asymmetries for specific nuclear excitations studied in (e.e'f) and (γ,f) reactions

Abstract

Two experiments establish an evidence for different fission fragment mass asymmetries for specific nuclear excitations: in near barrier photofission of 236U enhanced quadrupole contributions (fission through the J π = 2 + , K = 0 transition state) have been observed in the fragment angular distributions for a far asymmetric mass split. On the other hand, the fission decay of the isoscalar giant quadrupole resonance exhibits larger mass symmetric contributions than the E1 and E3 resonances as observed in 235, 238U(e,e'f) coincidence experiments, where the fission width ratios Γ s / Γ A have been determined as functions of excitation energy for separated multipole resonances.