Calculation of mean projected range and range straggling of heavy ions in polyatomic targets

Based on Biersack's angular diffusion model for the slowing down of ions in matter, an efficient method has been developed for calculating the mean projected range and range straggling of heavy ions in polyatomic targets. The method differs from both the Lindhard-Scharff-Schiott procedure and Monte Carlo simulation. Heavy ions such as Br+, Au+, Hg+ and Bi+ have been chosen. The targets ranged from diatomic to heptatomic, and included amorphous SiO2, quartz, polymers, Li0.16Na0.84NbO3 crystals, tungsten bronze crystals and seven-component glasses. In each case, calculated values are compared with experimental data at energies from 50 to 400 keV. Good agreement between calculated and experimental values of the mean projected range is found for the first-order treatment in Biersack's model; for the range straggling, the calculated values are much lower than experimental values in the first-order treatment. However, after considering the second order energy loss, marked improvements are obtained. (author)