Abstract
A model for the energy-loss function of a medium that is based on optical data ( approximately zero momentum transfer) and a quadratic extension into the momentum-transfer plane is used to evaluate the stopping power of the medium for protons and antiprotons. Energies less than approximately 40 MeV are considered for which radiative energy losses and density-effect corrections are negligible. 'Higher-order' corrections to the stopping power proportional to the incident particle charge to the third power, Barkas effect, and to the fourth power, Bloch correction, are included. Calculations are presented for aluminium, carbon, copper and polystyrene. Comparisons with experimental data indicate that the optical-data model, plus higher-order corrections, provides an excellent description of energy loss for proton energies from approximately 100 keV to several tens of MeV.