Quasi-free electron-ion scattering in ion-atom collisions

The Electron Scattering Model, ESM, for ion-atom collisions refers to the s cattering of a quasi-free (loosely-bound) target electron in the field of a highly charged projectile ion. Many atomic processes have been successfull y described by the ESM, which relates a differential scattering cross secti on for an ion-atom collision process to the cross section for the correspon ding pure electron-ion collision process. The following processes have been studied in ion-atom collisions: resonant and non-resonant electron-ion ela stic scattering, resonant and non-resonant inelastic electron-ion scatterin g, and dielectronic recombination. Recently, features have been observed in electron double differential cross sections from ion-atom collisions that have been attributed to "super elastic" electron-ion scattering, and intra- atomic double electron scattering in the case of molecular targets. Also ev idence for tripiy-excited states formed by resonance excitation has been ob served. A survey of the results of these studies and the status of this hel d of research will be presented.