The authors present a detailed description of a model calculation based on the Green function formalism for the electron-core-hole interaction at solid surfaces. It includes bulk and surface states and allows an exact solution for the contact exciton problem. Binding energies, oscillator strengths, wavefunctions and the absorption coefficient are evaluated with no approximations for different surface orientations of a simple cubic lattice. A large enhancement of the exciton binding energy is obtained in some situations, while in others binding is suppressed altogether in the first few planes, and a 'dead layer' results. The simple and exact model gives an insight into a broad variety of physical situations and experimental results.
 

Surface Science, 129 447-81, 1983.