The masses and kinetic energies of 239Pu fission fragments in the neutron resonance region and their relationship to dynamical effects in fission

The dissipation of the collective energy at the saddle point for neutron fission of 2 ^las been investigated by a measurement of ^^^Pu fission fragment masses and kinetic energies. Studies by previous authors on the amount of this dissipation contained conflicting results. The present measurements used neutrons in the resonance energy region where, for ^^^Pu, the relative fission contribution from individual (J,K,TT) collective channels can be calculated. The neutron energies were E^ = 0.033, 0.081 and 0.296 eV. A triple-axis spectrometer was used to provide a monoenergetic neutron beam. A thin, 12 yg cm""^, ^^Sp^ target was prepared by the method of electrospraying.