Ion scattering spectrometer utilizing charge exchange processes

An ion scattering spectroscopic method and apparatus are described wherein an oscillatory variation in the yield of ions scattered from solid surfaces provides information indicative of electron exchange processes associated with particular electronic states in the atom, which states vary with the electronic environment surrounding the atoms. The apparatus includes means for directing a beam of ions having a known mass and a known charge state toward a solid target surface such that an ion impinges thereon and scatters therefrom. During the impingement, the energy of the incident ions is varied over a range of predetermined primary ion kinetic energies. Ions having a given primary kinetic energy prior to impingement lose a given fraction of that energy upon elastic scattering from an atom of given atomic mass on the target surface. Accordingly, ions scattered from atoms of a single atomic mass are continuously detected by synchronously ''tracking'' the acceptance energy of an analyzer with the variation in the kinetic energy of the incident ions. A signal indicative of the yield of ions scattered from atoms having a single atomic mass is thus produced and when plotted as a function of incident primary ion kinetic energy, forms a spectrum wherein particular electronic states may be discerned