ABSTRACT
This chapter aims investigates the dynamic and static inter-electron correlations that can shed new light onto high-energy ion–atom collisions. The standard impulse approximation (IA) of Chew, derived originally for nuclear collisions, also invokes the impulse hypothesis but completely neglects multiple scattering effects. In the IA, the total scattering wavefunction is allowed to be distorted only by the field of the projectile, whereas the target nucleus is assumed to merely generate a momentum distribution of the initial electronic bound state. The IA of Chew for short-range interactions has attracted a great deal of attention in nuclear physics, since agreement with experimental data was consistently good. As an illustration, as well as for the purpose of assessing the validity and utility of the so-called ‘reformulated impulse approximation’ in comparisons with the IA, detailed computations of both differential and total cross sections are carried out for the prototype H+-H charge exchange at intermediate and high energies.
