For a number of experimental results obtained under well-defined surfa
ce and ion beam parameters, the mechanisms of ion-induced electron emi
ssion are identified. and approximate theoretical descriptions are pro
vided. Low energy threshold of kinetic ion-electron emission for H+ sc
attering off Cu(110) is explained by perturbation of localized electro
ns in collisions with target atoms. Electron spectra for H+ on LiF and
Ar+, Kr+ and Xe+ on Cu(110) are explained by electron promotion.