Energy Straggling of Helium Ions in Aluminium

Straggling of 3He+ ions in thin films of Al has been measured in the energy range 1.1 - 2.3 MeV. The energy straggling was obtained by taking the backscattering spectra of incident ions first from a clean Ta backing, then from an identical Ta backing onto which a thin Al film has been evaporated. The straggling values were compared with predictions of various theories. The results calculated by Bohr and Lindhard-Scharff theories are respectively 15%, and 30% lower than our experimental measurements, whereas those are in good agreement with the Rethe-Livingston theotv.