Spontaneous Fission Fragment Velocity Measurements and Coincident Gamma Spectra forCf252

Abstract

The velocities of both fission fragments from the spontaneous fission of ${\mathrm{Cf}}^{252}$ have been measured simultaneously with the pulse-height spectrum produced by the fission gamma rays in a large NaI(Tl) crystal. The average total kinetic energy before neutron emission is found to be 181.9 Mev with a full width at half-maximum of 17.5 Mev at the most probable mass ratio 1.33. The width has been corrected for neutron recoil and the average total kinetic energy for the effect of the angular dispersion of the fragments by neutrons. The yield of gamma rays shows a pronounced dip in the region where one of the fragments is near the doubly magic nucleus ${\mathrm{Sn}}^{132}$. There is a suggestion that the average gamma-ray energy is higher in this region. The correlation in number of gamma rays with total kinetic energy is very small and can be represented by $\frac{1}{〈N_{\gamma }〉}\frac{d{N}_{\gamma }}{d{E}_T}=-{{0.0029}_{-0.0011\mathrm{}}}^{+0.0007\mathrm{}} {\mathrm{Mev}}^{-1\mathrm{}}.$