Neutron-induced spontaneously fissioning isomers

Abstract

Experimental data on neutron induced spontaneously fissioning isomers are considered. To populate isomeric states of heavy nuclei in the uranium-berkelium region (n, n') and (n, gamma) reactions on actinide targets were used; (nano, micro and millisecond) pulsed beams offast neutrons were provided by the electrostatic accelerator facilities; time analysis was applied to fission fragment spectra to distinguish between prompt and delayed events and coincidence measurements to observe for the first time light charged particle accompanied fission (ternary fission) from isomeric state were accomplished. Measured values for fission isomer yields and obtained shapes for excitation functions find their explanation beyond the scope ofthe nuclear shape isomerism hypothesis, the latter being the in-thing for nearly 30 years. To tell two points apart the hints to quasiparticle, not the shape, nature offission isomers are discussed.