Due to the energy range typically used in ion scattering experiments (> 500 eV), effects of thermal vibrations, phonon oscillations, and interatomic binding are ignored since they are far below this range (~a few eV), and the interaction of particle and surface may be thought of as a classical two-body elastic collision problem.  Measuring the energy of ions scattered in this type of interaction can be used to determine the elemental composition of a surface, as is shown in the following:
Two-body elastic collisions are governed by the concepts of energy and momentum conservation.  Consider a particle with mass m, velocity v, and energy given as  impacting another particle at rest with mass m.  The energies of the particles after collision are  and  where  and thus .  Additionally, we know .  Using trigonometry we are able to determine
Similarly, we know
In a well-controlled experiment the energy and mass of the primary ions (E and m, respectively) and the scattering or recoiling geometries are all known, so determination of surface elemental composition is given by the correlation between E or E and m.  Higher energy scattering peaks correspond to heavier atoms and lower energy peaks correspond to lighter atoms.