The Effect of Inelastic Loss on the Development of Interatomic Collision Cascades

A theory of interatomic collision cascades in an infinite medium subject to inelastic energy loss (ionization slowdown) of particles is developed. Emphasis is on the angular and energy distributions of primary ions and cascade atoms upon slowdown. Analysis is performed under the assumption that single scattering of the particles follows the hard ball law, and the electronic stopping power of the medium is determined by the Lindhard formula. It is shown that the inclusion of slowdown directly in solving the Boltzmann transport equation radically changes the angular and energy spectra of the ions and cascade atoms obtained when the slowdown is ignored. Moreover, slowdown is the factor responsible for the anisotropy of the angular distributions of low-energy primary ions and cascade atoms.