Electron-loss calculations using the free-collision model

There have been very few measurements of electron-loss cross sections for high-energy (>1-MeV) negative and neutral hydrogen projectiles interacting with gas targets. Previous approaches to the estimation of these cross sections have been based mainly on semiempirical fits aimed at tying the existing low-energy data to theoretical high-energy Born approximation values. Such target-dependent approaches are reliable only for targets for which a sufficient amount of experimental data exist. The more general approach presented here is based on the free-collision model and uses global properties of the momentum-domain atomic form factor to calculate electron-loss cross sections. The results are simple functions of E and Z, with a small number of target-independent parameters. For each single-electron-loss cross section, ${\sigma }_{\mathrm{-}1}$,0 and ${\sigma }_0$,1, fits to available data are presented.