The energy spectra of atoms slowing down in structureless media

Abstract

Collision densities have been computed for a uniform, isotropic source of mono-energetic atoms slowing down by elastic collisions with the atoms of an infinite, homogeneous, structureless medium. It is found that, because of the indistinguishability of the particles proceeding from a collision, the results are relatively insensitive to the shape of the differential elastic scattering cross section, whether this is described by a Legendre polynomial expansion, or by the interaction of the atoms through the Born-Mayer or the Thomas-Fermi potentials. For energies not too close to the source energy, the collision densities vary as 1/E ², in agreement with the result for hard-core scattering and with certain available experiments.