STUDY OF STOPPING CROSS-SECTION FACTORS OF HE IONS IN SOME METAL FLUORIDE FILMS

Stopping cross section factors, [epsilon], of helium ions, in thin eva porated films of MgF2, LaF3, NdF3, and ThF4, have been measured by bac kscattering combined with optical methods. The measured values of [eps ilon] are compared with those calculated from the Bragg's rule using t he tabulated atomic cross sections. The differences between the measur ed and calculated values were as high as 17%, but the combined uncerta inty arising from the measurement and calculation is estimated to be l arger than this value.