Probing Interaction Potentials: Small Angle Differential Scattering of H⁺ and H with He

Abstract

Absolute measurements of heavy-particle angular differential scattering cross sections at keV energies and small angles permit determination of interaction potential energy curves and provide data required to model physical processes in plasmas and planetary atmospheres. Furthermore, these cross sections are typically so strongly forward-peaked that absolute small angle measurements contain the major part of the total cross section. The structure observable at small angles (due primarily to diffraction effects, classical rainbow scattering, and quantal interference oscillations) is also worthy of study in its own right. Despite the substantial body of data on angular differential scattering, there exist very few absolute measurements. A programme of measurement of absolute differential cross sections for scattering of atoms and ions was begun at Rice University in 1983. In this chapter, absolute differential cross sections determined by this group [5.1–3] for direct scattering of keV-energy H atoms from neutral helium and direct and charge transfer scattering of keV-energy H⁺ ions from neutral helium are reviewed.