How well does ⁴He backscattering from low-Z nuclei obey the Rutherford formula?

A study of ⁴He backscattering (150°) cross sections for O, Al, and Si atoms in the energy range 0.6-2.3 MeV has been completed. We conclude that the ⁴He backscattering cross section for these elements follows the E^-2 energy dependence of Rutherford backscattering to 1%-2% over this energy range. These results have significant implications for the use of ⁴He backscattering as a materials analysis tool for low-Z elements.