Recoil Properties of Fission Products

The range and relative rates of energy loss in Al and Au have been measured radiochemically for five products from thermal-neutron-induced fission of ${\mathrm{U}}^{235}$. Range-velocity relationships for the median light product of fission and the median heavy product have been obtained from these measurements and other workers' energy-loss data. The relation of range ($R$) to energy ($E$) or velocity ($V$) can be fitted to functions of the form $R=kV\ensuremath{-}\ensuremath{\Delta}$ or $R=K{E}^{\frac{2}{3}}$. We have assumed that these functional forms can be applied to fission products of any mass. The constants $K$ and $\ensuremath{\Delta}$ were determined from values of the range and kinetic energy for products of high yield. The values of these constants have been extrapolated to products of low yield. We have estimated kinetic energies, heretofore unmeasured, from the ranges of low-yield products.We have interpreted certain radiochemical observations in terms of the average component of the range perpendicular to the original velocity. The value of this component in Au has been estimated to be about one-fifth the total range.