Fission-fragment yields and prompt-neutron multiplicity for Coulomb-induced fission of 234,235U and 237,238Np

Low-energy fission of U-234,U-235 and Np-237,Np-238 radioactive beams, provided by the Fragment Separator (FRS) of the GSI Helmholtzzentrum fur Schwerionenforschung facility (GSI), has been studied using the Reactions with Relativistic Radioactive Beams / Studies on Fission with Aladin (R3B/SOFIA) setup. The latter allows us, on an event-by-event basis, to simultaneously identify, in terms of their mass and atomic numbers, the fissioning nucleus in coincidence with both fission fragments after prompt-neutron emission. This article reports new results on elemental, isotonic, isobaric, and isotopic yields. Moreover, the high accuracy of our data allowed us to study in detail proton even-odd staggering, from elemental yields; neutron excess, from isotopic yields; and total prompt-neutron multiplicity, from the difference of masses of the fissioning nucleus and fission fragments. These results are then compared to previous experimental data in order to probe how these fission observables change as function of the excitation energy and atomic and neutron numbers of the compound nucleus.

Automated summary

This study investigates low-energy fission of U-234, U-235, Np-237, and Np-238 radioactive beams using the R3B/SOFIA setup at GSI, and reports new results on elemental, isotonic, isobaric, and isotopic yields. High accuracy data allows for detailed analysis of various factors such as proton even-odd staggering and neutron excess in relation to fission observables.