Energy loss by nonrelativistic electrons and positrons in polymers and simple solid hydrocarbons

The energy loss and transport of electrons and positrons in gaseous cyclohe xane, and solid cyclohexane, benzene, polyethylene, and polystyrene are det ermined and discussed. A formalism for the energy loss properties of nonrel ativistic positrons, analogous to that previously developed for electrons, is presented. This approach makes use of the dipole oscillator strength dis tributions of the medium, which are constructed here for polyethylene and p olystyrene from their optical properties and from atomic X-ray photoabsorpt ion coefficients. inelastic collision cross-sections, mean free paths, stop ping powers, energy loss distributions, mean energy losses, and csda ranges are evaluated for electrons in gaseous and solid cyclohexane, solid benzen e, polyethylene, and polystyrene. Those properties depending on the zeroth energy moment of the inelastic collision cross-section are similar for the solid media, while those depending on the first energy moment show signific ant differences. The data for electrons are discussed and compared and cont rasted with the results of similar calculations for positrons. For energies greater than similar to1 keV, the energy loss properties of electrons and positrons are similar, but for lower energies there are very apparent diffe rences.