Neutralization of ions at surfaces

A theory has been developed to describe neutralization of ions colliding with solid surfaces. The theory encompasses adiabatic (resonance and Auger neutralization) and nonadiabatic processes, and incorporates effects due to energy, symmetry, localization, and lifetime of surface electronic states. The formalism is also applicable to ionization, excitation, and de-excitation processes. Application to 300-2500-eV ${\mathrm{He}}^{+}$ scattering from Cd, Ga, Pb, In, Sn, and Sb reproduces the recently observed oscillatory intensity spectra, and demonstrates conclusively that this behavior arises from a near-resonant charge-exchange mechanism. The theory helps to clarify the roles of various neutralization processes occurring at surfaces, it suggests some potentially interesting new experiments, and there is hope that in conjunction with experiment it may provide important information about the properties of solid surfaces.