Slowing of Fission Fragments in Noble Gases

Measurements have been made which give information on the slowing of ${}_{}{}^{235}{}_{}{}^{}\mathrm{U}$ fission fragments by gaseous and metallic-foil absorbers. Emphasis was placed on slowing of fragments by noble gases: helium, neon, argon, krypton, and xenon. The data show significant discrepancies from the existing theory, and suggest that it is necessary to take into account the effects of electronic shell structure of the fragment in treating the slowing-down process.