Dipole moments of the top and second layer ions of RbI(0 0 1) surface determined by high-resolution medium energy ion scattering

The heights of the top layer ions of RbI(0 0 1) surfaces from the second layer I− and Rb+ ions, respectively were determined directly by medium energy ion scattering (MEIS) with a monolayer depth resolution. The balance between a short-range force and a long-range Coulombic one gives the local electric fields at the relaxed lattice positions of the first and second layer ions. As the short-range interaction, we employed the pair potential which reproduces well the elastic constants of the bulk RbI crystal. Multiplication of the electric field by the polarizability (bulk) deduces the dipole moments of the top and second layer I− and Rb+ ions. The present MEIS results generally agree with the theoretical predictions based on the shell model.