Stimulated desorption by surface electron standing waves

The total electron-stimulated desorption yield of Cl⁺ ions from the Cl-terminated Si(111) surface is shown to exhibit fine-structure oscillations as a function of incident electron beam direction. We demonstrate that this fine structure is consistent with quantum-mechanical scattering and interference of the incident electron. Comparison of experimental data to a qualitative theory reveals the site of the excitation responsible for desorption, and the ground-state atomic bonding geometry of the desorbate. The data are consistent with desorption initiated by an excitation localized on the Si atom bonded to Cl.