Electric quadrupole giant resonance in the photofission of ²³⁸U

The ²³⁸U nucleus was studied measuring the electrofission yield and angular distributions of fission fragments, in the energy range of 5.5 to 28.3 MeV, using a new method of analysis. An E2 isoscalar giant resonance was found in the photofission cross section of ²³⁸U. This resonance exhausts (71 ± 7)% of the energy-weighted sum rule and is located at 9.9 ± 0.2 MeV with a width of 6.8 ± 0.4 MeV. The position of this resonance is in reasonable agreement with the Bohr and Mottelson prediction (58A^{-1 / 3} MeV). The width of 6.8 ± 0.4 MeV is compatible with a possible triple splitting of the resonance. From the angular distributions of photofission fragments and yield measurements of multipoles other than E1, evidence of an M1 mixture in the energy region 6-7 MeV was found.

NUCLEAR REACTIONS, FISSION Electrofission of ²³⁸U (e, e'f), E₀=5.5 to 28.3 MeV, measured electrofission yield and angular distributions of fission fragments. Deduced E2 cross section and E2 isoscalar giant resonance parameters.