Consistent definitions for, and relationships among, cross sections for elastic scattering of hydrogen ions, atoms, and molecules

Owing to the crucial role played by elastic scattering in various gas/plasma environments and to its fundamental nature, we consider in the present work low-energy collisions among isotopic variants of H⁺+H, H+H, and H⁺+H₂. In particular, we present consistent definitions of the elastic-scattering cross section and its common transport relevant moments regarding the quantum indistinguishability or classical distinguishability of particles, correcting some inappropriate definitions found in the literature. Further, we utilize a large collection of fully quantal calculated results for these systems to display the scaling relationships that exist among them.