NEUTRON EMISSION BEFORE FULL ACCELERATION AND THE SPECTRA OF PROMPT NEUTRON FISSION

The hypothesis that some or all fission fragments emit neutrons during acceleration is verified. It is shown that the kinetic energy of the fragment at the neutron-emission time (KEFNE) can be determined from t he analysis of neutron spectra in the laboratory system if their param eters in the c.m.s. are known. For Cf-252, these data were taken from the experimental studies; for other fissile nuclei, they can be calcul ated using the Cf-252 data and the Fermi gas model. For Cf-252, the ra tio of the KEFNE to the total kinetic energy equals 0.86. Although thi s value is close to unity, the time interval between the scission and the neutron emission decreases by a factor of over 10.