Resonant electron surface-barrier scattering on W(001)

We have examined very-low-energy electron reflectivity data for W(001) at an angle of incidence of 15^∘{} in the [10] azimuth. The structure of the surface barrier is modeled by a one-dimensional saturated image potential, and the metal substrate is modeled by a muffin-tin potential. We have found that below 10 eV, fine-structure surface-barrier scattering features are due to a resonance mechanism where up to seven internal scattering events occur between surface barrier and metal substrate. Previous detailed examinations of fine-structure features have led to the identification of only the interference mechanism in which the features are due to a single scattering between barrier and substrate. When the resonance mechanism occurs, electrons enter above-vacuum quasistable energy states of the surface-barrier potential. The confirmation of the resonance mechanism will allow a parametrized nearly-free-electron scheme to be used to analyze the experimentally obtained features and hence, possibly, to determine the lateral variation of the surface potential on W(001).