First investigation of prompt neutrons from spontaneously fissioning isomers produced in multinucleon transfer reactions

Le résumé fourni par la source

This work presents the first experimental results on prompt neutron multiplicities from short-lived spontaneously fissioning isomers produced in the multinucleon transfer (MNT) reaction of 26 Mg + 238 U. The observed prompt neutron multiplicity distribution yields an average neutron number of ν ¯ = 2.65 ± 0.20 and a variance of σ ν 2 = 1.4. The half-life of the spontaneously fissioning products was determined to be T 1 / 2 = 5 . 3 − 0.4 + 0.5 μ s . The shape of the multiplicity distribution of prompt fission neutrons was restored using the Tikhonov regularization technique and is characterized by a symmetrical distribution. Among the known spontaneous fission isomers, 239 m Pu and 243 m Am exhibit half-lives and prompt neutron multiplicities that agree with the measured values within uncertainties. GEF model estimates yield ν ¯ = 2.54 ± 0.20 for 239 m Pu and ν ¯ = 2.91 ± 0.20 for 243 m Am, with the former showing slightly better agreement. Whether the activity arises from a single isomer or a mixture of both remains unresolved, as the current data do not allow for a clear separation of their contributions. Further high-statistics measurements, including fission fragment total kinetic energy and gamma-ray spectroscopy, are required for unambiguous identification of the fissioning nucleus.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.