CHAPTER XIV - THE PASSAGE OF FAST PARTICLES THROUGH MATTER

Abstract

A fast charged particle in passing through matter ionizes the atoms, thereby losing energy. In gases, the ionization losses can be regarded because of collisions between the fast particle and individual atoms. In a solid or liquid medium, however, several atoms interact simultaneously with the particle. The effect of this on the energy loss by the particle can be regarded as resulting from the dielectric polarization of the medium by the charge. The energy loss by the moving particle is just the work done by the force exerted on the particle by the field that it produces. The energy loss per unit path length is the work done by the force over that distance; it is called the stopping power of the substance with respect to the particle.