Recoil momentum spectroscopy in ion-atom and photon-atom collisions

An overview is given on the use of recoil momentum spectroscopy in ion atom collisions, with particular emphasis on the longitudinal momentum transfer. The use of such spectroscopy for differentiating experimentally between electron-nuclear and electron-electron interactions in the collisional ionization of hydrogenlike O and F by a He target is discussed. A similar differentiation for He on He is described. The possible use of similar techniques for the study of photoionization and Compton scattering is discussed.