Survey of Stopping Power

This survey discusses the status of stopping power problems pertinent to dosimetry. It is shown that stopping powers of light elements can be predicted with high accuracy over wide energy ranges. A systematic discrepancy of ca. 2 per cent still exists between the stopping powers of heavy elements with high-energy particles, and those derived from measurements with low-energy particles. This discrepancy may arise from an underestimate of the stopping-power deficiency of inner atomic shells at low energies as introduced by the presently available theoretical inner-shell corrections. Only the Z-dependence of mean excitation potentials derived from high-energy experiments is in concord with the statistical Thomas-Fermi-Dirac model of the atom. The non-additivity of stopping powers can be incorporated nearly quantitatively in stopping power calculations by applying valence-state corrections to the mean excitation potentials of atoms.