Angular distributions of 12C, 14N, and 16O ion elastic scattering by sulfur near the Coulomb barrier and the high‐energy limits of heavy‐ion Rutherford scattering

Elastic scattering of 12C, 14N, and 16O ions by sulfur has been investigated near the non‐Rutherford energy threshold below 31 MeV. Angular distributions in the range 72°–170° have been measured. Decreasing elastic scattering cross sections with increasing angle above a threshold energy and smooth oscillations were observed. As a function of energy, the cross sections fall off rapidly above the threshold energy, rendering heavy‐ion backscattering spectrometry practically useless. A classical semiempirical model is introduced for predicting the angular and target dependence of the high‐energy limit for 12C, 14N, and 16O ion Rutherford backscattering spectrometry. The present energy thresholds are reproduced by the model within experimental accuracy.