Range and Range Dispersion of Specific Fission Fragments

The range and dispersion in range of specific ${\mathrm{U}}^{233}$ and ${\mathrm{U}}^{235}$ fission fragments; namely, those associated with delayed-neutron emitters, have been determined in gases of different atomic number. These measurements give the $Z$-dependence of the range and range dispersion for fragments associated with a specific mode of fission. After corrections for foil thickness and geometry the $Z$-dependent part of the range dispersion which arises from the nuclear stopping process was determined and values were obtained for the residual component corresponding to the energy dispersion associated with the fission process itself. The values thus obtained for this energy dispersion are found to be in fair accord with recent theoretical results of Fong.