Ionization of xenon Rydberg atoms at a metal surface

Experiments in which a thermal-energy beam of xenon Rydberg atoms is directed at near grazing incidence onto a flat Au(111) surface are described that provide new insight into charge transfer and electron tunneling during atom/surface interactions. Analysis of the data shows that for the present range of principal quantum number n, 13 less than or equal to n less than or equal to 20, ionization occurs at an atom/surface separation Z(i) = (4.5 +/- 0.9)n(2)a(0), where n(2)a(0) is the Bohr radius of the atom. This result is in good agreement with the value Z(i) similar to 3.8n(2)a(0) predicted by ab initio hydrogenic theory.