ELECTRON-EMISSION INDUCED BY RESONANT COHERENT INTERACTION IN ION-SURFACE SCATTERING AT GRAZING-INCIDENCE

The resonant coherent interaction of an ion with an oriented crystal surface, under grazing-incidence conditions with respect to a special direction of the crystal, gives rise to electron loss to the continuum from electronic bound states of the ion. The calculations presented below predict large probabilities for electron emission due to this mechanism. The electrons are emitted with well defined energies, expressed in terms of the condition of resonance. Furthermore, the emission takes place around certain preferential direct-ions, which are determined by both the latter condition and the symmetry of the surface lattice. Our calculations for MeV He+ ions scattered at a W(001) surface along the (100) direction with glancing angle of 0-2 mrad indicate a yield of emission close to 1. Using heavier projectiles, one obtains smaller yields, but still large enough to be measurable in some cases (e.g., approximate to 0.9 for 53 MeV B4+ and an angle of incidence of 1 mrad). Besides, the initial bound state is energy shifted due to the interaction with both the crystal potential and the velocity-dependent image potential. This results in a slight shift of the peaks of emission, which suggests a possible spectroscopy for analyzing the dynamical interaction of electronic bound states with solid surfaces.