Does backscattering of ⁴He ions by nuclei obey the Rutherford cross-section formula?

Implicit in the use of nuclear backscattering as a quantitative analytic tool is the accuracy of calculating cross sections using a classical Coulombic scattering formula (Rutherford cross section) which includes recoil effects, but ignores spin, nuclear size, electron screening, hard-sphere scattering, and any nuclear-force effects. The Rutherford cross section has not previously been verified experimentally for ions of 4He (1-2.5 MeV) for targets of 16O, 27Al, and 28Si. For 14N, agreement has been found with an accuracy of about 5%. Our experimental results show that 27Al and 28Si have the Rutherford formula value (±1%), and 16O is Rutherford from 1.4 to 2.4 MeV. 14N appears to deviate by about 2% at energies from 1.2 to 2.2 MeV and by more beyond this energy band. © 1974 American Institute of Physics.