Dissociation of polyatomic ions at surfaces: The influence of mechanical and electronic energy transfer

The dissociative scattering of CF₃⁺ ions from a clean Ag(111) surface was explored in the energy range 100--600 eV. Both negative (CF₃^-, CF₂^-, and F^-) and positive ions (CF⁺ and C⁺) were formed. The complete dissociation of the CF₃⁺ molecular ions into C⁺ fragments was found to be feasible at low (normal) incoming energies. We conclude that the breaking of three C-F bonds is due to concerted electronic and mechanical energy transfer. The azimuthal orientation of the crystal has a large influence on the degree of dissociation, which indicates the importance of direct momentum transfer. {} 1996 The American Physical Society.