Recoil effect on prompt neutron emission from 252Cf spontaneous fission fragments

The recoil effect for spontaneous fission of 252Cf has been calculated. An angular neutron spectrum has been calculated in terms of the evaporation model at angles 0, 90 and 180 deg for every fragment. The recoil effect and dispersion of angular measurements are shown to depend upon the fragment mass. For 0 deg angle, the recoil effect has a negative value and independent of fragment mass. For 90 deg and 180 deg angles, the kinetic energy of a fragment increases due to the recoil effect and strongly depends upon the fragment mass. The greatest recoil effect is produced on light fragments. If the recoil occurs from several neutrons, dispersion can be summed up and emission of each neutron can be considered as an independent process