THE RANGE OF Na24 IONS OF KILOELECTRON VOLT ENERGIES IN ALUMINUM

Abstract

Detailed studies are reported for the depth of penetration in aluminum of monoenergetic Na²⁴ ions over the energy region 0.7–60 kev. Below 20 kev the median range (R_M) increases linearly with energy as predicted by the Bohr–Nielsen equation. As was observed in a previous study with Cs¹³⁷ ions in aluminum, the experimental distribution curves are not Gaussian in shape, but consist of a markedly asymmetric peak followed by a pronounced exponential "tail". The results of a Monte Carlo calculation show that the observed distribution curves correspond quite closely to those predicted by an isotropic elastic-scattering model.Above 20 kev, a slight deviation from the linear range–energy relationship is observed; also, the distribution curves become narrower and more symmetrical, suggesting that electronic interactions are starting to play a significant role in the stopping process. Some preliminary results for the range of accelerated ions of Rb⁸⁶ and K⁴² in aluminum are also included for comparison. Median ranges for each of the alkali metal ions are compared with those predicted by the Bohr–Nielsen treatment.