Energy Loss of Fission Fragments in Light Materials

A calibrated silicon detector provided range-energy data for ${\mathrm{Cf}}^{252}$ fission fragments in ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, ${\mathrm{N}}_2$ and Mylar. Bohr's classical stopping-power theory and Lindhard's more recent Thomas-Fermi model both underestimate the measured energy losses. For both theories, the discrepancy with experiment is a monotonic function of the atomic number of the stopping material, at least for the limited range of materials studied.