Field Ionization near Nonuniform Metal Surfaces

Abstract

Four one‐dimensional, solvable pseudopotential models are employed to calculate the field‐ionization energy distributions outside of (a) step‐function clean metal surfaces (b) step‐function metal surfaces with a monolayer or less of adsorbed metallic or neutral impurities, and (c) clean metal surfaces with finite thickness and various shapes. All models lead to resonances for low‐energy ions. For the step‐function clean metal surface these resonances occur near the Bohr quantization energies for an inverted, infinite triangular potential. Both adsorbates and changes in the shape of the surface potential alter the intensity pattern of the resonances. A model in which the surface region is described by a linear potential leads to a two‐slit intensity pattern. Potentials with a finite discontinuity in the zeroth, first, or second derivatives all lead to slowly damped interference effects explicitly associated with the nonanalytic dependence of the potential on the position coordinate.