Ionization of xenon Rydberg atoms at oxidized Si(100) surfaces

The ionization of xenon Ryberg atoms incident at near grazing angles on an oxidized Si(100) surface is being examined. Comparison to earlier measurements at a Au(111) surface suggests that ionization, i.e., electron tunneling, occurs much further from the surface and at atom-surface separations that are physically unreasonable. A number of possible explanations for these observations have been considered including both ion reflection and the presence of stray electric fields at the surface. Model calculations suggest that even relatively small variations in surface potential due, for example, to surface charging can lead to the generation of strong local fields sufficient to field ionize the incident atoms before tunneling occurs. This effect is discussed together with possible applications in the detection of low-n Rydberg atoms.