Velocity and Angular Distributions of Prompt Neutrons from Spontaneous Fission ofCf252

Abstract

The velocity and angular distributions of neutrons associated with light and heavy groups of fission fragments from spontaneous fission of ${\mathrm{Cf}}^{252}$ have been measured. The results can be accounted for within about 10 to 20% by the assumption of isotropic evaporation from moving fragments. Least-squares fits to the data have been made on this assumption and yield accurate values for the numbers of neutrons emitted by the light and heavy fragments and for their energy spectra. The energy spectra have been analyzed in terms of effective temperatures of the fragments. A detailed discussion of the systematic differences from simple evaporation theory is given.