THE RESONANCE IMAGE STATES AT THE (111) SURFACE OF FCC-METALS

On surfaces of many metals the vacuum level is situated above an energy gap and therefore resonance image states can exist outside the energy gap. The (111) surface of a model fcc crystal, with the vacuum level above the upper edge of the energy gap L1 was considered here, allowing study of the influence of the crystal band structure on the energy spectrum and broadening of the resonance image states. Calculations, based on the Green function matching, were performed for different values of the matrix element of the crystal potential V111. It was found that for decreasing V111 (which increase the energy distance between the vacuum level and the upper edge of the energy gap) the absolute value of the binding energy of the resonance image state decreased. A comparison of this conclusion with experimental results was presented and discussed.