Collisions of ions with surfaces at chemically relevant energies: Instrumentation and phenomena

Abstract

An overview of gaseous ion/surface collisions is presented, with special emphasis on the behavior of polyatomic projectile ions at hyperthermal collision energies (1–100 eV) and the instrumentation needed for such studies. The inelastic and reactive processes occurring during ion/surface collisions are described in terms of several archetypes, viz., elastic and quasielastic scattering, chemical sputtering leading to release of surface material, inelastic scattering leading to surface-induced dissociation (SID) of the projectile, ion/surface reactions, and soft landing. Parameters that are important in ion/surface interactions are discussed, including the interaction time, the conversion of translational to internal energy, the translational energies of the scattered ions, the effects of scattering angle, and the influence of the nature of the surface. Different types of tandem mass spectrometers, built specifically to study ion/surface collision phenomena, are discussed and the advantages and disadvantages of the individual designs are compared. The role of SID as a technique in bioanalytical mass spectrometry is illustrated and this inelastic collision experiment is compared and contrasted with gas-phase collision-induced dissociation, the standard method of tandem mass spectrometry. Special emphasis is placed on reactive scattering including the use of ion/surface reactions for surface chemical analysis and for surface chemical modification.