Study of stopping cross-section factors of He ions in some metal fluoride films

Stopping cross section factors, [ε], of helium ions, in thin evaporated films of MgF₂, LaF₃, NdF₃, and ThF₄, have been measured by backscattering combined with optical methods. The measured values of [ε] are compared with those calculated from the Bragg's rule using the tabulated atomic cross sections. The differences between the measured and calculated values were as high as 17%, but the combined uncertainty arising from the measurement and calculation is estimated to be larger than this value.